Do you make money with social networking sites like Twitter and Facebook?

Tweet

I know that there are a lot of different ways to make money with sites like Twitter and Facebook, but I was wondering how you make your money with these websites. I've made some money on Twitter by linking to one of my websites, but I'm just starting to get a feel for Facebook. I know about this app: http://apps.facebook.com/referquest/ that might help me to make money, but does anybody know of anything else?