Spammers are betting that sponsors don't talk to each other, and they're right. So if the spammer gets shut off by one sponsor, he can go abuse another one.
The end result is that mainstreamers get upset with spam when they see that a lot of it has adult content — while those businesses that are Can-Spam compliant and use good business practices get caught up in the net.
Do spammers get upset when someone spams them?
Brandon Shalton rants about patent abuses at FightThePatent.com and operates T3Report.com