A bit of background: 4chan.org is an extremely influential segment of the web population. You've heard of LOLcats? Rick-rolling? Chocolate Rain? Those memes started on 4chan. Despite their influence over net.culture, 4chan is very underground, hidden ... a bit seedy, if you will. But seedy with an ethic. Seedy in kind of a cool, punk rock sort of way. For example, 4chan is home to an online group called Anonymous that isn't afraid to take on Scientology.
Nevertheless, you probably wouldn't bring 4chan home to Mother. NSFW and potty-mouth can be found all over the site.
But I'll be damned if I think AT&T should have the right to censor them. When information can be blanked out memory-hole-style by common carriers, then we have a very serious problem. Where does it stop? Do common carriers have the right to stop the flow of information they find offensive? Who decides what is 'offensive'? What if there is net-speech that criticizes their company and hurts their bottom line?
This is nothing less than the digital equivalent of book-burning. If you are a common carrier -- and you are not China or Iraq -- then you'd better behave in a fashion that supports full, open and transparent communication. This is an extremely stupid move on the part of AT&T and should be vociferously condemned -- no matter what you think of 4chan.
AT&T, I do not need you to tell me what I can view or not view. That is not your place.
True, 4chan is a little dirty. But AT&T censoring them is even dirtier.
If you'd like to follow the next moves of 4chan, which promise to be ... interesting, they've set up a Twitter feed here: http://twitter.com/4chan4ever.