XKCD (one of my favorite webcomics online) came up with an idea for an IRC bot that would mute anyone if they posted something that had been posted before. The purpose of this was to insure that there would always be original content in the chat room.
4Chan, after dealing with their most popular image board degrading into a slurry of continually reposted memes, decided to apply the same princible from XKCD to a new image board, and /r9k/ was born. So far, it seems very effective and the result is a /b/ that kindof works again.