By a narrow 3-2 vote, the Federal Communications Commission (FCC) has ruled that Comcast was in the wrong when they dialed down bandwidth or interrupted transmissions altogether among their customers using file-sharing programs such as BitTorrent. Comcast and other ISPs maintain that since they spend billions every year maintaining their networks, they should have the right to curtail bandwidth hogs. This ruling instead sides with the end-user, who pays for the right to send and receive whatever they like across the network in question.
Despite several members of Congress — Illinois Senator Barack Obama among them — trying to put together Net Neutrality legislation, so far there is no actual law in place governing these proceedings. As such, no specific fine has been issued, nor action taken against Comcast other than to order them to stop filtering their users' traffic based on the content or method of transmission. This order gains its power from a policy adopted in late 2005, which included principles to ensure broadband networks be available to everyone at a fair price, and without restrictions. Various grassroots organizations have been pushing for an official Net Neutrality law to be put into effect so that these types of interventions can be punishable. With this ruling, the other big telecom companies like AT&T, U.S. Telecom, and Verizon are saying this is good enough, and that we don't need specific laws.
While peer-to-peer file sharing is commonly associated with the illegal piracy of software, music, movies, and other media, it remains a legitimate means of sending and receiving files, regardless of what is actually being sent or who legally owns the rights to it. The reason Comcast gives for taking any action to begin with is due to the fixed allocation of bandwidth. Essentially, the more high-bandwidth file-sharing there is on their network, the slower everything becomes for all users, not just the ones doing the sharing.