Need your advice please - About a new social network

Hey,

Quick question : Is it a good idea that users on a new social network are given some space at the right side of their profile post their own ad banners?

Letting the users post their own ad banners which is out of your control is not a good idea. What if 100 thousand users post porno pics on their ad space? It'll go down real fast like orkut. The ads should be posted and controlled by you, not them. That's how you make money by owning a social network.