One thing we spend a lot of time thinking about here is how someone who just joined Facebook figures out what to do next. Almost everything on Facebook centers around friends—sending messages, checking out photos and profiles—all of these things are pretty boring without any friends.

We realized that people who are already on Facebook know who should be friends with whom in ways that we could never figure out. So, for example, if John joined Facebook and became friends with Sally, Sally would probably already know a few people who would want to be friends with John. We built the "Friend Suggestor" so that Sally could do just that.