Pirate bay is free to the public, the others are Private and require you to keep ratio (share) and do not come with viruses or crappy audio or horribly tagged files like PB.
If you can post being a power user in two non-demnoid private sites, I might consider digging up my account that I don't use anymore and send some educational invites. I had the misfortune of getting screwed by association through inviting someone on here that didn't know (or care) that cheaters always get caught sooner or later.
