I personally say, "fuck warning the sites". If your stuff is up there, sue them.
As soon as my video is up on any finnish sharing site, I'll call up the cybercrime squad and spill my beans. No polite emails asking them to remove the stuff. Fuck them hard.
..now, I can only do that to finnish sites really. I'm not gonna call russian/german/argentinian cops if I find my stuff there.
We need RIAA for adult videos.