Player and RP enthusiast Saphrona of the Shadow Council server has compiled all the known information about pirates in Azeroth. Most of the information comes from the WoW pen and paper roleplaying game. Blizzard lore guru Chris Metzen has approved all the lore added to the game by the PnP books, so it's as good as gold.
Saphrona has dug up some interesting facts, such as there are more pirate organizations in the game than just the Bloodsail Buccaneers. Roaming the high (and low) seas of Azeroth are:
The Blackwater Raiders
The Southsea Freebooters
The Southsea Pirates
The Defias Brotherhood
Also, the Bloodsail Buccaneers are using engineering to secretly construct a submarine fleet and the leader of the Bloodsails believes so strongly in human supremacy of the high seas, that he refused to aid the Alliance in the Third War. Scurvy dog, indeed.
For your pirate lore overview, check out Saphrona's full article on the official forums.