I always judge things by considering the risk/reward.
I am usually the first one to say "fuck the rules" so let's just take the CanSpam Act out of play for a moment. Think about what is contained in a supression list.
1. People that said, hey don't send me any more mail.
2. Seed accounts for advertisers as well as affiliate networks.
3. Honeypots from anti-spam orgs.
4. The SCREAMER lists! you always want to avoid that...
Doesn't sound like a list that is easily monetized, does it? Couple the shitty list with the current mail enviroment and you aren't going to make very much. So that's the reward part of the risk/reward.
Although one may think that the biggest risk would be the CanSpam Act and the government, I believe the biggest risk lies in the SCREAMER file. I know most major networks have shared the known addresses of several rings of people who continually sue mailers for violating the CanSpam Act. By grabbing the suppression list you almost guarantee that you will be hitting these traps. There's the biggest risk that I see.
Other risks include not getting paid by the network/advertisers. Again, most major networks have seeds and/or use a monitoring services such as LashBack to monitor their suppression files. When they notice you hitting traps on their suppression, you can almost be certain that you are not getting paid for that traffic and probably getting a kick in the ass off the network.
So the risk is high. The reward is almost non-existent. I vote -- I think you should try it. I just wouldn't.