I'm surprised an ad-network hasn't risen up offering to promote the ads others won't; tobacco, alcohol, drugs, weight loss, pyramid schemes, you name it. Some m

I'm surprised an ad-network hasn't risen up offering to promote the ads others won't; tobacco, alcohol, drugs, weight loss, pyramid schemes, you name it. Some might be legally unavailable, but I don't see what's stopping a rogue advertising network from engaging in the practice.