The entertainment industry has won a famous victory. The US Supreme Court made a unanimous decision that file-sharing services can be held legally responsible for distributing products to facilitate illegal downloads. That is a big boost to film and music companies’ fight against online piracy. On the publicity front alone it sends a clear message to users that file-sharing is illegal in most cases. But it remains one battle in a long war.

Take the detail of the ruling. The Supreme Court made it clear companies such as Grokster would be held responsible if they “induced” users to infringe copyright. However, the court left open the possibility that companies could provide a product allowing users to, say, share files - as long as illegal use was not expressly promoted and the product had significant legal uses.