This article has it all laid out in a semi-convincing way. It's good fodder for discussion but it could also be a valid point.
http://www.chron.com/cs/CDA/ssistory.mpl/editorial/outlook/2430461
Personally, I like the idea. It's hard to believe Clinton would put his ego aside long enough to even say yes to an offer. But then again, I've seen the guy a couple of times since he left office and he looks bored as hell.
He's a divisive figure and we're a divided nation. He'd shake up the race (preferably in late spring) and being a VP candidate would make his already high fund-raising prowess almost dubya-like. He would also be a great point man for restoring international relations.
As we've seen with Cheney, the most powerful man in the WH can indeed stay out of the spotlight just fine. I know I'm smokin the windowshades here but why not???