How to bring down 4chan

http://xkcd.com/591/

while this is just a comic, it does implicate a very real method to flood a particular site with a particular fanbase.

Also, xkcd has become a driving force on the site digg.com where almost every single update is brought to the front page (something very hard to do in its own right). this is very similar to pagerank in such that xkcd has a very high rank among digg users and is voted for consistently and quickly