re Pirate Bay - I had not checked to seeif the website was up and running, but went on chatter I had seen that various torrent tracker sites (which I assume only record details of how many machines are sharing data) had stopped working.
Useful input, MmeBodyInTheBasement - I can understand the 'unusable' viewpoint. There are many factors which affect how well the torrent facility works, including how many other people are actively using that torrent (someone with the complete file(s) would be 'seeding'), and whether your ISP has some form of traffic restriction when using peer-to-peer.
Some set very low limits during the "peak hours" of internet usage. With many services that might mean 0800-0000 - the peak hours for household usage being the evening, while ISPs don't want their network too slow during the business day.
Torrent traffic may make up 50% of all data transfers for some ISPs and I saw some truly shocking graphs a few years ago which showed the extent of the problem.
It is a problem for ISPs as they need to manage their networks and limit traffic to some extent as they are charged based on volume, so have to know whether they are making a profit, breaking even, or might make a loss!
It may have been 'unusable' for you, but clearly it can be different for each ISP and for each torrent (as a high number of others with the same torrent would mean the download could go much faster).