This is still something Facebook should solve. Facebook, despite its public groups and pages, still fosters incredibly insular communities, and those can get tedious very quickly. The reason Tumblr and Twitter have any popularity is that they encourage finding and following new, interesting people. They have a lot more novel content and it's easy to explore and find more of it. If Facebook gets seen as the boring, traditional social network (which to some degree it has), then that seriously damages its credibility.
Yes yes yes. There's a huge unsolved problem in the social networking space: meeting new people near you (for purposes other than dating or sex, but that too)
That'll be the next truly big thing, I think. It might focus on places or events, like connecting people who are going to a concert or a bar. That's sort of what I hoped FourSquare would be, but it's even more insular and boring.