Right now we automatically match users similar to Facebook Graph, but we do it specifically on things people care about - people nearby who share your interests, hometown, classes, industry, etc. Our app is also university-only at the moment to filter out the creeps. We've also recently experimented with a location-based group chat feature in order to promote local interaction.

I wouldn't categorize this issue in the same domain as Facebook though. Facebook is about two things -- sharing and friends. There's a mental divide between the friends and strangers, so users would never use it to meet new people. There's already platform to share things between strangers (reddit), but a platform to "interact" with strangers (which is what facebook used to do, but with friends) still has yet to emerge.