It appears that 5300 names, address, emails, and IP addresses of Sky Broadband subscribers have been leaked out. These 5300 individuals were at some point in a porn piracy investigation by ACS: Law.
The story goes like this. ACS: Law has made a career out of finding, fining, and/or suing pirates of copyrighted material, because of this members of 4chan put them in their cross hairs. The people of 4chan were able to hack ACS:Law's website and steal several personal emails one of which contained this list. Then through the ebb and flow of the internet the list has ended up on The Pirate Bay where it is being shared by hundreds of people.
This fight highlighs several problems in the current fight against piracy. These people have not been convicted of anything and yet they are now finding themselves exposed to all sorts of drama. If you're going to fight piracy make sure that your own website is hacker-proof please.