The BT ruling is worrying because it turns ISPs into censors, and of course copyright infringement isn't the only kind of content people would like to block.
We've had calls to ban sites that espouse extreme political views, sites that promote anorexia, sites that discuss ways to commit suicide. If BT can block Usenet archives, why can't it block everything that anybody thinks is unpleasant or undesirable - like WikiLeaks, or anti-Scientology sites, or anything that isn't appropriate for under-fives?
Crazy? Look at Australia, where child-protecting politicians seriously proposed an outright ban on all online content that wasn't suitable for children. If it wasn't behind an age verification system, the politicians said, ISPs should block it completely.
http://www.techradar.com/news/internet/isps-are-now-the-internet-police-984628
I agree that it's a slippery slope.
Rather than trying to stop piracy, why don't they provide a service that we actually want i.e. an easy way to buy and listen to music whenever and wherever