On "social networking", I guess. Just like with instant messaging, Facebook has a monopoly on social networking thanks to network effects. User join Facebook because all of their friends are already on Facebook, which leads to even more users joining Facebook.

Its the same scenario we saw with AIM in the instant messaging space. Lots of people were already on AIM (thanks to having AOL accounts), making AIM an attractive choice for new users. The trend was only broken when the AIM protocol (as well as those of other proprietary chat networks) was broken, allowing multi-protocol chat clients to bridge the gap between networks.

We're already seeing the same thing with social networks. Many clients support both Facebook and Twitter, allowing users to transparently bridge the gap between the two largest social media networks on the Internet.

Like quanticle said, social networking. You can't say, "fuck this, I'll just integrate with myspace instead" without getting laughed out of the room. Like it or not, Facebook's the only game in town.