Yeah, I remember blowing into my 2600 games all the time. When the carts aren't seated right, instead of the blinking blue screen like on the NES, the 2600 gives you that hip pinstripe pattern with the high pitched whine.
I blow on my DS games occassionally. Logically, I know it doesn't really do anything, but it's just second nature at this point.
...word is bondage...