Friendster and Myspace didn't have a chance to figure out a way of making money that earns billions a year. Facebook has. That is why - Facebook is now in a position to not wither away like Friendster and Myspace. But thats just my opinion.
You can see that Google is more or less established not because they are making billions but because there's an "eco-system" of companies who make money along with Google and can be expected to keep pushing that money long term back to Google. The same might (or might not) be said about the iPhone. But you'd be hard pressed to find anything like a stable ecosystem grown-up around Facebook. The only thing that grows on Facebook seems to be social games and those depend on FB's own growth. The claim of social network sites has been that they can sell focused eyes. But I haven't seen evidence that they can sell social eyes that will do anything.
It seems like even without a competitor, Facebook will become Yahoo in a few years - not dead but a site that can charge very a premium for ads or experience.
But hey, I'm just guessing...
Claims for Facebook making billions seem exagerated to me.
Facebook isn't going to make money just by knowing general things about you. It still needs to be there when you are looking for something.
What do I care how targeted an ad is when I'm not at a location to buy things to begin with.