My first time out i was new only ever played paintball and i have to say it should be common sense not to shoot for the head first off cause it its a small target compared to the rest of the body second is it can hurt people and isn't nice to do it intentionally. But i will be the first to admit that if your not gonna call a hit on ur chest or back and i can hear the hit off ur mag or armour then yes i will pop u one in the head. I also agree with Danke on your head is very often what you lead with and is also the last part to get back into cover as well so head shots are almost a given.
At the same time though when u stand up got both hands up no hand on your weapon and are yelling hit and the guy looks at you and puts a burst into your face then ya u got every right to get a lil ticked. Now im not saying go rip his face off but a "hey dumb ass look and think before you f***ing shoot"is more than warranted.
So my point is dont be a prick and shoot for the head/face intentionally but don't be a bitch either