This was truly fascinating and hilarious. I didn't know what the word 4chan meant, after reading a blog post somewhere that mentioned it. So, I looked it up on trusty ole Google--which led me to trusty ole Urban Dictionary--so here's a direct cut and paste, you just have to read this (beware adult themes and language):
you have just entered the very heart, soul, and life force of the internet. this is a place beyond sanity, wild and untamed. there is nothing new here. "new" content on 4chan is not found; it is created from old material. every interesting, offensive, shocking, or debate inspiring topic youve seen elsewhere has been posted here ad infinitum. we are the reason for "not safe for work". we are the anonymous army. cross us and you will fail. anonymous is everywhere. you depend on us every day. we bag your groceries, we fix your computers. anonymous sees you before you see him. sitting at desks around the world right now is a nameless, faceless, unforgiving mafia composed of the best of the best.
we are 4channers. the people devoid of any type of soul or conscience. products of cynicism and apathy, spreading those very sentiments daily. anonymous is the hardened war veteran of the internet. he does not forgive or forget. we have seen things that defy explantions. heard stories that would make any god-fearing, law abiding citzen empty their stomach where they stand. we have experienced them multiple times and eagerly await their return.
4chan is a place of sheer genius and utter stupidity, and there is often a thin line dividing the two. here you will see a state of mind that exists in most human beings, but is rarely if ever shown. this is a place where taboos do not exist. 4chan cannot simply be regarded as a simple website or imageboard. it is so much more than code. 4chan is alive and constantly changing. this is a subculture, a self-governing sect of the world. rich in history and foundation. to become a 4chan user is to speak a different language. to leave behind any methods of conventional thinking you once knew.
there are things here that you will not understand and things you never will understand. if you cannot accept this then GTFO now. because there is no turning back.
this is 4chan
The sphincter of the internet.
Where integrity goes to die.
...look, another anonymous middle aged fucktwit on 4Chan posted some more pics of cartoon babies having sex...
A message board and image board on the Internet where people congregate to post various kinds of pictures, flash animations, and discuss things such as anime. It is the English version of the original Japanese board with a similar system: 2chan.
The system that 4chan uses is Anonymous, so one can safely post one's opinion without worrying. One can use a name and a tripcode (a # followed by a 'password') to gain 'status' on 4chan.