An informal experiment by staff of the Associated Press indicates that at least one ISP is actively blocking user access to the popular BitTorrent protocols used for filesharing. This is a challenge to Internet neutrality and freedom to access.
Whatever your opinion on the legality and copyright issues of this technology, this means of data transmission and filesharing has been embraced by many companies and open source projects. Universally blocking subscribers from using this protocol clearly ignores the fact that torrents and other P2P programs do have legitimate uses.
So, unless the ISP in question is looking at the content of the files themselves (a violation of user privacy), then they are indiscriminately blocking access with no clear justification for such behaviour.
Read the ars technica article here.
UPDATE: posted 25 October 2007
The ISP in question has claimed that it is not acitvely blocking torrent traffic, but simply "delaying" such traffic to reduce lag time for more important data packets.
Here is a related Globe and Mail article.