*bump*
Interesting thread, I'm going to hunt through my log files right now...
The (recent?) fusker 'feature' of indiscriminately hotlinking a numbered range of images caused a lot of problems on one of my sites, because they img src'd a php script rather than the images which it displays. The end result: 250+ rapid-fire loads of a PHP script within a few seconds by each fusker surfer. Some of them even reloaded since all of the images showed as broken.
One quick fix for fusker dumbasses who try to hotlink HTML scripts rather than images might be to check the http_accept variable - if the browser is expecting an image rather than HTML then abort the script (or 302 to a suitable 'fuck you' image

)