Difference being facebook realisticly is not a big money maker, it makes money soley based on one thing that it does not do as well as investors would like. GM just pulled a $10M in ads off facebook because they don’t work.
Only way ads are going to generate the revenue investors are going to want to see is if they make it a pop up or throw it all over your timeline which in turn will piss people off turn them away. It’s happend multiple times, all it takes is a few people to move to another social network, their friends to follow and then it slowly trickles till its dead… happend to myspace and many others