> but I really believe that the next "big social thing" will be a start-up that will somehow make it easy to approach people you don't know and spark up a conversation.
Absolutely. This is a particularly acute pain point for us nerds, but it afflicts just about everyone to some extent. Our social circles are unfortunately limited in a way that technology could certainly address.
I envision a service that would include everything from dating to finding Dungeons & Dragons groups to just finding people to chat with who are currently nearby and share an interest. Google Glass would make this kind of thing even more interesting.