PeerPong was incubated by the VC firm Partech International and was originally called Muchobene. CEO Ro Choy, who was formerly chief revenue officer at RockYou, joined this January. The company has raised $2.8 million from DCM, First Round Capital, Charles River Ventures and Partech International.

Out of the more than 100 million Twitter users, only about 3 million of them have demonstrated “real knowledge,” said Choy in a recent interview. That’s according to PeerPong’s “PeerRank,” which uses natural language processing to analyze what you tweet about in order to identify your areas of expertise. So for instance, Choy pointed out an alpha PeerPong user named Ian Manton from the UK who loves technology and has answered about 60 questions about phones and software for the site.

Here’s PeerPong’s own description of how it’s different from other Q&A services — particularly the Google-owned Aardvark, which seems similar but looks to users’ extended social networks and their self-stated interest areas to solicit answers:

PeerPong doesn’t rely on friends of friends or feel-good motivations to deliver a fast answer, or crowd-sourcing to find a “best” answer. Instead, PeerPong looks for the best person for a specific question and empowers and incentivizes knowledgeable people in a variety of ways to encourage them to share their expertise.

PeerPong currently uses its own Twitter accounts to message relevant Twitter users to ask them to respond. It will soon give its questioners those potential answerers’ Twitter handles so they can address messages themselves. These methods could quickly turn spammy for so-called experts who’d rather not be PeerPong users, but we’ll have to see what happens now that the site is public.

Users who register for PeerPong to participate as experts can earn badges and get widgets to solicit questions on their own blogs. And users who ask questions have the opportunity to ask follow-up questions and engage with experts directly.

I’m not sure much of what people talk about on Twitter could qualify them as subject-matter experts, even if PeerPong’s natural language processing is awesome. I mean, does the fact that you tweet about where you eat every night make you a restaurant guru? Maybe. Still, the company might have a good middle ground with people who want to style themselves as experts. They’ll earn on-site reputations points, recognition and perhaps traffic directed back at their own projects — and at some point PeerPong should probably pay them a cut of whatever it’s making.

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PeerPong isn’t open to the public yet, but the service describes itself as “an easy way to connect with the right Twitter users to get direct answers fast.” Its presence on Twitter explains “Please ask us your question by DM (d AskPeerPong) and we will match you to Twitter users who can provide timely relevant answers.” (DM means direct message, Twitter’s method of sending private correspondence to another user.)

That’s quite similar to Aardvark, the social search startup Google just bought for a reported $50 million. Building such a service through Twitter does make it a little more idiosyncratic: I can’t yet ask PeerPong a question because you can’t direct message accounts on Twitter that don’t follow your own account (as of today AskPeerPong only follows 1,229 people). By contrast, Aardvark uses your Facebook connections, with questions inputted on its own mobile, web and IM apps and then sent to relevant friends and friends of friends who’ve been identified through Facebook Connect.

PeerPong is led by Ro Choy, who was in charge of business development and revenue for RockYou before leaving late last year.

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