It is widely considered to be an abuse of tor. The system wasn't built for that from a technical perspective, and from a social perspective, you are degrading the quality of the service for the people who actually need it.
because it makes it so difficult to provide exit nodes in the US for people that actually need them. DMCA complaints will quickly take down an exit node because of tor users sending bittorrent traffic out of it.
Just like DMCA complaints have shut down other internet service providers, like Comcast? Ultimately, in the US, ISPs are not responsible for their users' activity. "Common carrier" and all that. When you open an exit node, you become an ISP.
i'm aware of DMCA's safe-harbor provision and i've fought with colo providers over it. when you're not an ISP the size of comcast (or any decent-sized "real" ISP), you're always going to be subject to another company's AUP.
i've had an exit node shut down by a colo provider simply because they didn't want to deal with the overhead of processing the DMCA requests. they knew what tor was and they knew i wasn't the one downloading content, but they just didn't want to deal with it, so it was either turn the exit node into a relay or have my server shut off.
