AT&T is definitely blocking 4chan, but the reasons are not clear (see second update below). Perhaps this will turn out to be an overreaction. If so, that would be great.

I'm not a big fan of 4chan. I don't spend any time there. It's a cesspool. While it's been influential in its introduction of memes to the web (like the Rickroll, LOLcats and more), it's clear that /b/, the only portion censored, is a reservoir of the worst kind of filth, depravity, and yes, probably genuinely illegal content. I've lived on the Internet for over a decade and am a naturally curious person, so I'm pretty hardened to awful images, but /b/ is as bad as it gets.

However, that doesn't give AT&T permission to censor 4chan, or anything else. AT&T probably thinks starting with 4chan is a shrewd move on their part -- its denizens are annoying and its content unambiguously objectionable. It will struggle to find defenders. But it's clear that once they've set the precedent with 4chan, they will attempt to extend it, probably in directions that cut off file-sharing and other activities that are expensive for its network. In the long-brewing war over network neutrality, this is an opening shot, much less subtle but significantly smarter than Comcast's throttling of BitTorrent traffic 2 years ago.

It cannot, under any circumstances, be allowed to stand. AT&T is a private company, and has no moral or legal authority to decide what data I can and cannot send and receive. They are a big dumb pipe, and they should act that way or lose my business, preferably along with a lawsuit or two.

Censorship of the Internet is not a new development. Close to 100% of Internet access in the UK is quietly and effectively censored by the Internet Watch Foundation, a charity set up by the government and acting on government policy to maintain a list of illegal sites, primarily those hosting child pornography (although the law does not restrict it to this). The most effective part of this censorship is that it's so light-handed that many UK citizens are not even aware that their access is being "filtered".

Not so with /b/. 4chan is very popular (500,000 unique monthly visitors), and even /b/ is filled with overwhelmingly legal content. Not content in good taste, or polite, or of intellectual value, but certainly legal. And the rest of 4chan is unblocked, and full of messages complaining about the blocked portion. More importantly, 4chan has a disproportionate cultural influence and is notorious for having users who are prone to violent overreaction, as the Church of scientology has discovered.

The government is the only body I trust to censor anything, since I know if I disagree with their policy I can vote them out of power. Even then I am hugely wary of government censorship, though I made my peace with it in the UK. Unlike the UK's mostly uncontroversial CleanFeed system*, however, AT&T's move is unilateral, and without government mandate of any kind. In fact, since the the President has publicly declared his support for network neutrality, it's in direct opposition to stated government policy, if not yet any actual law.

Censorship makes me deeply, viscerally angry, a political position that I find I have in common with most geeks. Something about working with and manipulating data every day molds the conviction that access to information should be as free as possible, irrespective of other political affiliations. My favourite quote on the slippery slope of censorship is even more geeky -- it's from Star Trek:

With the first link, the chain is forged. The first speech censored, the first thought forbidden, the first freedom denied, chains us all irrevocably.

4chan is the first link in a chain that they hope you won't notice until it's wrapped around you, and by then it will be too late.

* Cleanfeed does not currently censor any part of 4chan, as of this evening.

Update: 4chan has already begun to strike back, planting thousands of fake reports that the CEO of AT&T has been found dead in embarrassing circumstances.

Update 2: Is there possibly a technical reason behind 4chan being blocked? It seems highly unlikely that blocking a single subdomain in this way would have the desired effect, though I am not a network engineer of any kind.