WHOA.
Just kidding. I know it's a serious issue.
RevShare Hosting: Why not offer a financial incentive to your users if they catch someone else doing bad stuff?
Additionally, if you put in your TOS that in the event a user is found pulling some dirty scumbag crap their personal info will be posted on an area of your domain.
A wall of shame page or something.
I guess the gist is to offer incentives to recruit your userbase to help be your eyes and show you won't screw around with anyone who gets caught by maintaining your own blacklist history available to anyone who wants to see it.
Also, how about a cheater/cloaker/theif e-mail form for LL owners and TGP owners to be able to *quickly* fill out.