It's good for things like "who wants to do <X> tomorrow?" where you're looking to get a crowd together that includes people beyond your close circle of friends.

It's good for things like "who wants to do <X> tomorrow?" where you're looking to get a crowd together that includes people beyond your close circle of friends. It's good for tracking what photos are uploaded of you. People don't think for a second that somebody might not want their photo online and they're going to do it anyway. I might as well know what's out there. Most useful for me, it's good for finding out what's going on in my city. A lot of people just forget to invite somebody if they're not on FB.