How popular? Well, the company said it has now hit 90 million users, adding 20 million in just over two months. Those users are now spending more than 1.5 billion minutes on calls and sending over two billion text messages each month. And the messages should keep on flowing now that Viber is adding group messaging with Viber 2.2. available on iOS, Android and on the BlackBerry beta.

Group messages has been around for a while, so Viber is coming late to the party. But group messaging on Viber comes with a smart notification feature to limit new message alerts. There’s also a simple system for starting group messages, which can include text, photos and location.

The 2.2 update also includes an HD voice engine to improve call quality and reliability and the ability for users to add photos to their contact lists. And for Android users, Viber offers support for Arabic, Chinese, French, German, Hebrew, Portugese, Russian and Spanish with expanded language support coming soon to the other platforms.

Communications apps like Viber are scaring carriers, who are seeing some of their most profitable services undercut by over-the-top services. Viber’s fast growth will only ratchet up fears that users will reduce their dependence on voice and texting plans. It’s going to force carriers to get creative with pricing, something we’re seeing with the new shared family plans from Verizon and AT&T. 

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This is yet another sign of the growth of over-the-top messaging services that utilize mobile data services on smartphones. While companies have often relied on SMS through providers like Sybase 365 to interact with consumers, marketers are evolving with their consumers, who are spending more time in apps on smartphones. With the Sybase Push 365 messaging service, Sybase 365 can offer a full suite of mobile messaging services beyond just text messages.

Under the partnership, Urban Airship will provide Sybase 365 with developer tools and resources to help its customers integrate push messaging into their apps. Sybase 365 customers will also get an online dashboard to create and analyze their messages. Interestingly, Sybase 365 said it will also be offering the services to its 900 carrier customers and OEM partners.

Greg Dunn, VP of product strategy at Sybase 365, told me he doesn’t see the addition of push notifications as a threat to traditional SMS and MMS messaging. Instead, he said it gives marketers another tool to interact with consumers. Push notifications have unique capabilities that allow companies to send out more dynamic messages than SMS with rich media, longer text lengths and the ability to redirect a user to any point in an application.

For Urban Airship, the partnership should provide a big bump in usage. Sybase 365 delivers 1.8 billion SMS and MMS messages a day. Urban Airship notched its 10 billionth message in January after launching in 2009 and now the company is up to 19 billion messages sent.

Though Dunn believes that traditional text messaging will continue to grow, I have to believe that the rise of in-app messaging will help slow that growth. We’re already seeing some operators with declining SMS revenue thanks to messaging apps. Sybase 365 is smart to prepare for a day when marketers send more messages through push notifications, which are cheaper than traditional text messages. This won’t happen immediately and text messages will still serve a role for enterprise customers. But as the world moves toward more in-app communication for both text and voice, that means companies like Sybase 365 have to adapt.

Disclosure: Urban Airship is backed by True Ventures, a venture capital firm that is an investor in the parent company of this blog, Giga Omni Media. Om Malik, the founder of Giga Omni Media, is also a venture partner at True.

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This is despite the fact that RIM still has a much larger installed based than Windows Phone 7, and Skype, which Microsoft bought for $8.5 billion, is now finally in beta on the Windows Phone platform. Lahman said even with the competition from Skype, Windows Phone is just an elegant platform that creates great user experiences. And that will allow TextPlus to compete well against Skype.

“The second we saw the OS and (Nokia) Lumia devices, we knew we wanted to support it,” said Lahman. “It’s a beautiful OS with a fresh take on what a phone OS can look like and that’s motivation for us to innovate. The OS brings elements that would be buried vertically to the top and you can see all your conversations, communities and contacts lists very easily. And you can pin specific conversations to the home screen. It’s elegant, easy to use, and it puts all of the elements at your fingertips.”

TextPlus, which connects to traditional PSTN phone systems, allows people to message for free using a dedicated phone number. It has racked up 27 million registered users and is now doing 110 million messages a day and has recorded 27 billion messages sent to date. In December, it got into the voice game with the TextPlus Free Calls VoIP for iOS and Android.

Lahman said TextPlus looked at launching a BlackBerry app a couple years ago, but couldn’t get it up to the quality level it wanted. And then when RIM announced a shift to a new operating system, Lahman said the company put further development on hold until it can get a better sense of what BlackBerry 10 looks like. But even as TextPlus waits, Lahman said it’s pretty clear that Windows Phone will be third place competitor in the market and should eventually displace BlackBerry.

“We didn’t need to be convinced by the numbers but by the user experience,” he said. “I would bet on Nokia and Microsoft to bring some powerful momentum here. These are some hungry organizations.”

Lahman is impressed with the slick panoramic view inside WP7 apps — the Metro user interface — allowing people to swipe between screens rather than click on tabs. And he said even the ability to personalize the app with same accent color from Windows Phone is also a help. Microsoft isn’t funding the app, but Lahman said it is providing some marketing help. That speaks to Microsoft’s continuing need to pursue marquee apps for its smartphone platform, which is now up to more than 70,000 apps.

These kinds of decisions to support Windows Phone over BlackBerry highlight some of the ongoing challenges for RIM. Even though ComScore reported that BlackBerry has 15.2 percent of smartphone users in January, way ahead of Windows Phone at 4.4 percent, RIM still trails in the mind of some developers. An Appcelerator/IDC developer survey published in November found that developers had begun showing significantly more interest in Windows Phone than BlackBerry for the first time. Things are looking up with some more support for the BlackBerry Playbook tablet OS. BlackBerry App World app store is now up to more than 60,000 apps and RIM reported that 13 percent of BlackBerry developers make more than $100,000 from their apps. But with BlackBerry 10 not expected to launch until late this year, RIM stands to lose more ground to Windows Phone among smartphone developers.

Again, RIM may still turn things around with BB10. And TextPlus is just one developer. But the battle for third place will be affected by who can amass the most developer support. RIM can’t afford to be the fourth choice for developers or passed over because of the perception that  developers can make better apps on rival platforms. It needs to keep attracting developers or the future that observers like Lahman predict will become a reality.

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Want to pay less than $1 for phone calls? Shell out for an iPod Touch and make sure you’re near a Wi-Fi network. It’s possible with a new app from Gogii, the maker of popular messaging app TextPlus, which is launching a new service called TextPlus Free Calls that enables a host of devices, even Wi-Fi-only devices, to make and receive phone calls for free or very cheaply.

With TextPlus Free Calls, users will be able to make unlimited free phone calls to other TextPlus members. And because TextPlus connects to traditional PSTN phone systems, users can connect directly to regular phone numbers at rates starting at 99 cents for 40 minutes without a contract or plans. Free trial minutes will be available to users who sign up. Devices like the iPod Touch will now be able to serve as phone replacements through Text Plus Free Calls running over Wi-Fi.

There’s some caveats but it’s another sign that Wi-Fi calling is getting bigger and a lot easier for consumers. But it’s not just for Wi-Fi only devices:TextPlus can help cell phone users reduce their voice minutes to the lowest plan while running their calls over Wi-Fi and 3G data.

The iOS app, which is separate from the TextPlus Free messaging app, is available now and will be in the Android Market shortly. Users will be able to use one account across multiple devices and will be able to access their call history and voice mail from any device.

The move pits TextPlus against a growing number of IP-based communications competitors, dubbed NUVO or Network Unaffiliated Virtual Operators by Sybase.  Many of the group text messaging services fall into this category and a smaller number of providers also offer voice services, some that come with their phone number like Google Voice and Pinger’s TextFree and others like Viber that don’t. By connecting to the PSTN, Text Plus Free Calls can send and receive calls to and from phones that don’t use the app.

The rise of these services are forcing traditional carriers to rethink their business models. The messaging apps are helping wean users off SMS text messages by connecting users directly over the Internet. And voice services are increasingly offering direct connections that allow users to forgo highly reliable phone calls and monthly data plans, for pay-as-you-go voice services that can offer free or very cheap calls.

It presages a future where voice is just an app on the data network, something carriers themselves are also slowly learning. Sprint has teamed with Google Voice to let people use their Google Voice number while AT&T recently released an International VoIP calling app. Republic Wireless, a division of Bandwidth.com which connects Pinger and Google Voice to the PSTN, recently launched Republic Wireless, offering users a $19 a month voice and data plan that relies heavily on Wi-Fi calling.

Scott Lahman, CEO of Gogii, said carriers can still compete on delivering 4G and high quality, reliable phone service. But he said there is a growing market for simple voice calls that can connect people. And that will change what consumers need from their carriers: fewer or no voice minutes and lots of data. Carriers such as T-Mobile also appear to be responding, offering a plan with just 100 minutes and data.

“We’re on the cusp of the most interesting time in the brief history of mobile,” said Lahman. “The internet has not done its thing in mobile until recently.”

TextPlus, which launched in 2009 and has hit 20 billion messages sent to date, also provides social elements inside its communications apps. Gogii has raised $28 million to date including a $15 million round earlier this year.

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Fast Society’s co-founder Matthew Rosenberg told me the company saw the writing on the wall at South by Southwest this past spring, when a number of messaging apps went head to head at the show. While the market seemed white hot, Rosenberg saw the limits of how far he could go with the group text messaging model. Rather than throw itself into the next version of the app, the New York-based team started plotting a new product, one that harkens back to the original vision for Fast Society.

“We originally thought of Fast Society as a way to save moments and capture experiences together but because of the circumstances and the competition, we got caught up in group text messaging,” Rosenberg said. “So much of it was about the technology but when we got to SXSW, we realized it wasn’t a tech problem, it was an experience problem.”

Rosenberg said the group messaging space has become saturated and the products have become fun features but not good businesses. Fast Society was one of the early pace setters and introduced things like including voice calls and sharing pictures and location. It was among the first to strike deals with brands, partnering with companies like MTV and others.

But Rosenberg said the business has low barriers to entry and some of the monetization models including like sponsored groups or advertising based on what people were texting wasn’t attractive. More fundamentally, he said there’s only so much that can be done through group messaging. And now that companies like Apple and Google are moving into the space while Facebook bought Beluga and Skype bought GroupMe, it becomes even less attractive for a start-up.

“It’s been a great place to build our chops and it’s been a street brawl with other companies, but we saw that the barriers were getting lower and no one was really winning,” Rosenberg said.

Rosenberg is tight lipped about what the future holds but he said it will explore emotions and experiences much more deeply. The company continues to survive on $380,000 in seed funding it received last year and has enough to launch Cameo.

Some of Rosenberg’s words could be looked as the parting shot of an entrepreneur who couldn’t keep up in the group messaging space. But he raises some good questions about how many companies can really succeed in the space and whether it can support stand alone businesses or is basically a feature that will replicated by bigger companies. WhatsApp, a company I profiled, has been thriving but it’s unclear how many others can join them. Also, it’s a good lesson on what happens when start-ups begin chasing fads rather than remain focused on their original passion. Rosenberg sounds like he’s fired up again. We’ll see if the plucky start-up can make a go of it on the rebound.

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