A new Apple patent is going around that offers up something called "iGroups" functionality -- it seems to be a kind of location-based social networking, including an ad-hoc currency functionality between a crowd of Apple devices. It's pretty interesting, though it sounds more like an idea Apple is playing with than an actual service they're going to debut. They specifically mention rock concerts and tradeshows (including WWDC), with the plan that someone would start up a "group," and then individual group members in the same location (determined by GPS) would be able to hook into that group and/or exchange contact info or "tokens" with other members of the same group. Not quite a Foursquare or Facebook competitor (this definitely seems like a much more local service), but a new kind of ad-hoc network based on the idea that everyone in the area who is using an Apple device can connect up in new ways.
The "token" idea is interesting, too -- it adds a gaming element to the situation that seems very un-Apple. That, more than anything else, is what makes me think this is Apple just covering their bases rather than securing an idea that they plan to put into action. Still, a lot of Apple's services (MobileMe, iWork, and so on) tend to be more traditional rather than innovative -- they innovate on hardware and often play catch-up on software -- they do it well, of course, but their specialty is polish, not necessarily. Diving into a newer arena like social networking would be an interesting move for Apple.