A recent chart posted by cnet shows that Facebook apps are primarily used "just for fun." And there have been a number of blog posts lately (particularly The problem with Facebook) which trash Facebook, saying that the site is effectively pointless and not worth any money.
Allow me to step forward in defense of Facebook.
I know people who spend a lot of time on Facebook. Who use those silly little apps. And who are looking at the ads.
Granted, the apps haven’t figured out how to make money yet. Same was true of the web circa 1995; lots of websites, most of them look-at-my-cat pages, and almost nobody was making money yet. It took a little time.
This is like complaining that Penny Arcade is useless and worthless because of its silly humor. Doesn’t matter; it can still make money.