This isn't some first person shooter game. Notch said that he's not adding blood. Fighting isn't the primary purpose of the game. Building is.
there's no primary purpose, you can do anything you please, that's the point of a sandbox game, also it is in first person, and jeb's in charge now, so his rules, but it's also technically a kids game, so blood would be better off as a mod or something.
Can`t see the dragon well? Take a closer look here: PLANET MINECRAFT
I don't think blood effects should be in Vanilla. I have a blood plugin for my server, though. xD