Vine now has a 17+ age rating and a warning that the app may contain mature content, and it also has a new tool to report inappropriate content or individual users as part of an update first spotted by The Verge. The changes were part of an app update.

The situation was handled far differently for 500px. The photography app, which had been available for download on the App Store for several years, was given a warning from Apple during a review of one of the app’s updates that there was possible pornographic content. 500px said they would look for and remove the content, but then the app was removed from the App Store altogether, and Apple claimed it received complaints of pornography involving children.

Though 500px maintains it never found and was never show examples of images involving children, 500px’s app was put back into the App Store after working with Apple over a few days to institute the company’s requested changes. Those adjustments included stricter search filters for images containing nudity and — like what Twitter added to Vine — a 17+ rating on it and a user reporting tool.

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The incident was one of the most high-profile in recent memory of an iOS app getting booted from the App Store over inappropriate content and — combined with the concerns over explicit imagery on Twitter’s Vine app released just days later — served to highlight the inconsistency with which Apple sometimes applies its App Store reviews process.

“It’s been a very intense week,” COO Evgeny Tchebotarev told me by phone on Tuesday. In the days since 500px was removed, he said his team has worked very closely with Apple to address the company’s concerns and get the app back online as quickly as possible.

The app has millions of downloads, and has been on the iOS App Store for several years. But it was seemingly caught off guard by Apple’s public comments last week that not only was the app in violation of Apple’s rules on any pornography, but an Apple spokesman said the company had received complaints about pornographic images involving children, which caused Apple to remove the app immediately.

Tchebotarev said Apple has still not given his company any evidence of explicit images containing children, nor has Apple given any examples of the complaints cited. In the last week 500px performed its own internal audit and found nothing, he said.

“This is something we are waiting to hear from Apple, if they can send us anything becuase this is a serious issue, criminal activity” that his company would report to the proper authorities if found, said Tchebotarev.

While 500px does not allow pornography to be posted on its app or on its website — users who do post it have their accounts deleted and images removed — it does allow “photos of an artistic nature that contain nudity.” 500px has always come with a safe search option by default that filters any images with nudity. But at Apple’s request, 500px is now filtering searches as well. “We made it harder [to find]. If you search ‘porn’ or ‘nudity’ you get zero results,” said Tchebotarev.

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After a bit of confusion over why a popular photography app was pulled from the iOS App Store early Tuesday morning, Apple offered up an official explanation: it had no choice but to pull the app because of some complaints of child pornography viewable within the app.

“The app was removed from the App Store for featuring pornographic images and material, a clear violation of our guidelines. We also received customer complaints about possible child pornography. We’ve asked the developer to put safeguards in place to prevent pornographic images and material in their app,” an Apple spokesman said in a statement Tuesday evening.

Oleg Gutsol, CEO of 500px, told GigaOM that Apple never mentioned any complaints about child pornography and that the company would not allow it on the app anyway. “We  never received any official complaints of child pornography. We don’t allow pornography on the site,” he said. “If it ever happened, we would have reported it to the police immediately.”

From the version of the story of the app removal 500px’s COO Evgeny Tchebotarev told Techcrunch, it’s not clear he was aware of the child porn claims either, just a general violation of the pornography rule.

The Apple reviewer told the company that the update couldn’t be approved because it allowed users to search for nude photos in the app. This is correct to some extent, but 500px had actually made it tough to do so, explains Tchebotarev. New users couldn’t just launch the app and locate the nude images, he says, the way you can today on other social photo sharing services like Instagram or Tumblr, for instance. Instead, the app defaulted to a “safe search” mode where these type of photos were hidden. To shut off safe search, 500px actually required its users to visit their desktop website and make an explicit change.

Gutsol said that his company had only heard from Apple it was easy to find nude photos with search terms like “nude” and “naked.” 500px made changes to its app and resubmitted to the App Store, but that update is still awaiting approval, he said.

Apple has been (mostly) clear from the beginning that it doesn’t admit apps that promote excessive violence, pornography or attacks on religion to its App Store. Steve Jobs himself called it Apple’s “moral responsibility to keep porn off the iPhone.”

While there can be different opinions of what constitutes artistic nude photography versus pornography, when children are involved, there’s no wiggle room. If Apple received such a complaint, it had to take the app down.

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In addition, Pinterest enabled in-board play for Kickstarter, Slideshare and Soundcloud, “so you can curate great collections of projects, presentations, and sounds, and play them right there on your boards.”

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Screenshot of 500px for iPad (click to enlarge)

Updated. 500px, the photo-sharing website beloved by photography professionals and highly skilled hobbyists, debuted a new iPad app over the weekend. And at just three days old, the new app is already experiencing growth that’s downright jaw-dropping.

Here are some of the numbers relayed to me by 500px co-founder Evgeny Tchebotarev:

• Users flip through an average 80 photos per visit to 500px for iPad, spending 35 minutes in the app
• The iPad app now serves 50 percent of all traffic seen by 500px’s website
• The app is on track to serve more than 1 million flips on Monday alone
• 500px for iPad is currently the top free photo app in the Russian app store, #3 in Canada and #4 in the United States

As we wrote when we first covered the Toronto-based startup back in May, 500px is known for having a slick user interface that complements the kinds of artistic photos hosted on the site. It makes sense that 500px’s experience would work so well on a design-centric device like the iPad. Also, a lot of the folks who love 500px are the same kind of early adopting, gadget loving power users who have fully embraced the iPad — it’s a perfect overlap of user bases.

500px for iPad screenshot (click to enlarge)

500px’s growth spurt

Overall, 500px has hit its stride in recent months. The site has grown by over 20 times in the past year, and continues to grow more than 30 percent each month — right now, 500px fields 3.4 million unique visitors monthly. As of today there are more than 2.5 million artistic photos on the site that have garnered more than 55 million page views. In the beginning of this year 500px’s only employees were its co-founders, Tchebotarev (who is also known by his artistic pseudonym “Ian Sobolev”) and Oleg Gutsol. Now the company has 12 full-time employees and is keen to hire more developers.

But it’s taken a while to build up to 500px’s apparent overnight success. 500px was first established eight years ago as a community for photography buffs within LiveJournal, the pioneering social blogging website. Its current incarnation as a wider scale photo sharing site was launched nearly two years ago, in late October 2009.

A small company — for now

Update: Despite all the growth, 500px has thus far avoided taking any venture capital investment on millions in venture capital. The site’s main revenue source comes from $50 per year premium accounts; 500px also collects a 5 percent commission on prints of photos sold by users. “We are well into generating revenue that helps us support the growth and expansion, and have new interesting products in the pipeline,” Tchebotarev said, explaining why they have yet to take on more outside funding than its $525,000 Series A. But he added: “Obviously, we are open to discussions.” With the kind of growth the company has seen thus far, 500px may start fielding offers that are hard to refuse.

This post has been corrected to include 500px’s Series A venture capital funding information. 

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