G+'s Circles are a killer feature and they alone make me hope G+ takes off. Circles solve some very entrenched problems in social networking. So I really hope Facebook is working on a quality response to that.
I think Facebook has had groups for a while - they just aren't exposed that well in the UI. (I don't think I've ever tried to use them, though, so maybe they're different from Circles in some way.)
Yeah but the key difference is G+ is pushing Circles upfront and hard from the get go. They are also implemented far better than anything Facebook has done along these lines. To truly get the benefit of Circles, not only do I need to be able to take advantage them but all my friends need to be using them too. If everyone is on board and using Circles effectively, the amount of noise overall goes down, and signal can go way up.
