Blizzard isn't exactly an upstanding corporate citizen

If you look at the history between Blizzard and their customers that do things they don't like (i.e. don't play the game in a normal way -- try to reverse engineer it, develop new content and gameplay, etc.), you'll find a long series of legal intimidation tactics.

Blizzard and their overenthusiastic legal team are really the RIAA of the computer gaming industry. They have no reservations about using legal threats and scare tactics, sending lawyers to peoples' homes, DMCA notices to people who reverse engineered parts of the game, etc.

They were also one of the first few companies to cause DMCA case law, in the Bnetd case ( http://www.eff.org/IP/Emulation/Blizzard_v_bnetd/ ). Strange thing is, people still seem to love them. The players (angry at people exploiting fundamentally broken game mechanics) jump up and down in joy as Blizzard tramples all over peoples' rights and sets dangerous legal precedent. I guess games and e-loot are Serious Business.