Allow members to monetize their blogs?

[-Om-]

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?

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