(..) Blizzard won’t take unnecessary risks, and this can be seen in the studio’s ability to cancel a game when it needs to be cancelled.

“We don’t release the failures,” said Morhaime, explaining how Blizzard has managed to maintain an unblemished track record. "The worst thing that we can do is release a game that’s not up to our quality expectations." (..)

from: DICE: Blizzard’s Building Blocks of Success. Very true and interesting since the launch of this company, It's just funny than in the list of cancelled game, they didn't included Ghost :P