I poison their requests with crap, particularly because they were the worst offenders for sheer request rate. The site has maybe a hundred pages, and I'd see them hit at a sustained 20 rps for weeks on end, same content being pulled over and over and over again. Easily handled by my small server as it's static content, but the sheer arrogance (inadvertent or otherwise) pissed me off.
I'm not sure if they caught on, or just finally started behaving better, but after months of being served crap in my never ending labyrinth of auto-generated junk, they have stopped.
