reply to MJB
Re: How Long Till Canada Gets A Copyright Alert System As bt mentioned, false positives are a problem but unsecured routers can also lead to problems. Since an IP address alone can't identify someone, there's no way to prove who actually shared a file. They would have to hold people accountable for not securing their network and many people don't know how to do this.
For those who share copyrighted material, this will just be a minor inconvenience. Some of them may decide to pay $5-10/month for a newsgroups subscription or for a VPN account to mask their IP while transferring files. Some people may decide to use anonymous P2P networks instead.
Technology continuously changes and when there's a need for anonymity, new types of file sharing technologies will emerge. The entertainment industry continues to play the whack a mole game and the only people who benefit from this are lawyers. Artists don't receive a cent from any of the lawsuits.