Shooting your finger?

I've been thinking lately about this, has any one ever heard of someone accidentally shooting their finger. I know when I shoot iI tend to stick my index finger out so that the arrow rests on that aswell as the thumb. I've started to worry that I might over draw and shoot it accidently. Has any one heard of this and is this a habit I should get out of? maybe i'm just paranoid? I have seen some pictures where people draw so much it looks very possible.