Well, I'm saying this but I'm not based on any data, it is just my opinion. You will find tons of computer illiterates on Facebook and MySpace. When I say tons I really mean it. Those users, based on my observations, really have a higher ad-click rate but social networks at the same time have a low click rate. When surfing those sites people are usually just "wasting" some time and they know what they are looking for: they wanna know more about life of others...