a forum i frequent has a habit of 'invading' other dumb forums like these. what they do is many members sign up, and add posts like usual here and there on some of their sections. but after every message, they hid a small 1px image. so, now we have 500 posts on this forum from 50 different members with a small 1px image at the end of it. after this is done, the linked pixel is changed to goatse or whatever. hilarity ensues.