Allow members to monetize their blogs?
 

I've been toying with the idea of allowing my subscribing members to monetize their blogs by allowing them to have ad space. The main question, as I see it, is .... what practical problems might I run into? Would I run into trouble with Google, for instance, if my site were to suddenly find itself hosting/running multiple Adsense campaigns from different users?

Still not sure about this, so any feedback/perspective, particularly from anyone who might have tried this already, would be greatly appreciated.