Noam says Obama shouldn't debate McCain in unmoderated forums:
McCain has several big disadvantages vis-a-vis Obama. He faces a massive enthusiasm gap and will have trouble attracting large crowds. He's in all likelihood going to be massively outraised and outspent, making it hard to get his message out. And, possibly as a result of the previous problem, he'll be cast as a right-winger determined to continue George Bush's policies.
The unmoderated debates would help him overcome all three problems. They'll draw big crowds and generate lots of buzz. They'll help him get his message out for free. And, just by virtue of appearing frequently at Obama's side and having a civil debate, they'll make him look much more moderate than the Obama campaign wants him to look.