Yahoo (NSDQ: YHOO) is making another social networking move, but at least this time, it isn’t trying to re-create the wheel by launching a distinct social net. At the Web2.0 Expo yesterday, CTO Ari Balogh introduced Y!OS (Yahoo! Open Strategy), a platform that will allow developers to tap into the millions of Yahoo accounts that users have set up across its properties (Mail, IM, Sports, etc.). For users: A richer, app-filled experience on Yahoo if all goes according to plans. Attempting to create a social networking experience on top of established user accounts isn’t exactly a new idea. Google (NSDQ: GOOG) has been trying to make its services (GMail, Reader) more social for awhile. Way back when, AOL (NYSE: TWX) tried building a full-fledged social net out of AIM with AIM Pages, though that looked mainly like an attempt to build a MySpace clone—not what Yahoo is doing.

(We’re going to hear more about this from the network and content side when Jeff Weiner, EVP of Yahoo’s Network Division, speaks at EconSM Tuesday in Los Angeles. )

News.com: “Balogh discussed the technical architecture--known as YOS, or Yahoo Open Strategy--including an application platform that will allow developers to create apps for consumers to keep their data protected and to chose what data to share and with whom. In addition, Yahoo will unify all profiles for users and developers, which will allow the company to leverage the 10 billion relations and 500 million users to create the social graph of relationships and to manage the event stream (what Facebook calls the Newsfeed). “We are not creating another social network. We will rewire the entire experience to make it social. We don’t think of social as a destination but as a dimension,” Balogh said. Along with Google and MySpace, Yahoo is a member of the OpenSocial Foundation, which is developing a specification for building social applications. “

Yodel Anecdotal: “There’s a massive, latent social network within Yahoo!, and we’re going to bring it to the surface. We’re making Yahoo! more social, but we’re not building yet another social network. We already have an incredible social network… we just need to unlock it. We are rewiring Yahoo!, building platforms that fundamentally change how Yahoo! works. We’re also opening up to developers to take advantage of the social aspects of our many favored destinations, creating what we call “vitality” — a lifeline into what’s happening with your social connections We plan to become open the best platform on the web, where tens of thousands of developers will create applications and features (many we’ve never even thought of) for our network and our consumers.”