Yeah, they have this youtube partners program. http://www.youtube.com/yt/partners/
It ends up being something like $5 per 1,000 unique views. Most of the spammers are idiots who haven't figured out basic math ratios though. What they usually do is copy popular videos, make a secondary link and hope no one notices, then spam it enough that hopefully one of theirs gets picked up somewhere as the real thing. Other times they legitimaltly are posting a real video, but its still spamming so it still gets nuked.