Why do ISPs even bother try to shut down BitTorrent? It is not the protocol that makes people share files. If file-sharers had to they would be sharing files over SMTP. Instead the media companies and ISPs should be using BitTorrent as a way to reduce their distribution costs.
Because it's very bandwidth efficient. It will try to maximize the bandwidth it has available to download and upload which ISP do not want. Sustained 100% usage of your bandwidth is not what they optimize for.
BitTorrent moves the bandwidth load towards the street-level networking gear, which is expensive to upgrade because there's lots of it. The copyright lobbies just give them a convenient excuse for getting rid of the problem.
Because lots of people only can BitTorrent. If you stop BT, then lots of your customers who are using bandwidth will give up and get their pirated files elsewhere. A dedicated advanced minority will not.
The purpose of blocking isn't to block all pirating (which it fails at), but to significantly reduce bandwidth (which it does).
