Google has come under fire of late due to the inconsistent nature of the adwords network in relation to allowing the spread of Spam and Trojan sites. Whether this criticism is fairly leveled is another matter. I have discussed this at length previously and as pointed out by Miles Burke, maybe Google is now promoting blog comment spam.
Now I was thinking on this the other day, the problem is that Google has a mainly automated system for adwords registration and delivery. I suspect they randomly dip into the pool of advertisers and manually vet them from time to time. I also would imagine that you would have matching analysis on the adwords and resultant advertisers site, and that this is applied again at random or to risk locations or information areas.
