Earlier this year, a lot of speculation came out about one of the U.S. largest ISPs interfering with or blocking BitTorrent traffic. Very little information came out of the company itself, though now the rumors and speculation have been proven.

It seems that Comcast has developed a technology that uses fairly dubious tactics to halt the flow of torrents and other types of file sharing. False traffic is generated that can prevent one end or the other from communicating. Their goal at the moment is simply to stop or slow uploads: Downloads proceed as normal. Unfortunately, the very essence of peer to peer, including torrents, is that you are downloading from another person. Thus, if many large ISPs were to follow Comcasts example, standard P2P would be greatly crippled. What upsets some is the apparent deceit Comcast uses to accomplish their goal of slowing P2P traffic:

Each PC gets a message invisible to the user that looks like it comes from the other computer, telling it to stop communicating. But neither message originated from the other computer --- it comes from Comcast. If it were a telephone conversation, it would be like the operator breaking into the conversation, telling each talker in the voice of the other: "Sorry, I have to hang up. Good bye."
There's a rhyme and reason to their apparent madness. Obviously, abuse of P2P can result in networks becoming overladen with traffic. When it comes down to choosing between traffic such as web surfing, email and VPNs over file sharing, an ISP truly has no choice and file sharing will get the bum end of the deal. This is a bone of contention to many Comcast subscribers, as P2P, particularly torrenting, has an increasing number of good uses. Many companies are beginning to use torrents to redistribute files like patches, trailers, installers, et cetera.