I stumbled upon Facebook's advertising page - http://www.facebook.com/ads/create/. One can choose various demographic parameters based on which Ads will be targeted. The nice part about this is that it shows the target audience size as you choose the values for the parameters. Numbers are always interesting. It is a known fact that not always the user declared demographic information is accurate. This seems to be the case with Facebook too.
Child marriage?! :-P
So, to what extent can one rely on user declared information? The question of trust is their on both sides - how can users trust service providers and how can the service providers trust their users?
By the way, Valleywag had reported sometime that now Bill Gates is "really" on Facebook.
