Why NOT to let a guy open the door...

I'm sure you've seen one of these on the top of doors... we have them at my university.
Anyhow, i was walking towards the parking lot with some of my friends, and i was at the front of the procession with my friend Michael. Well, we came to a door, and he kindly opened it for me....but very, very fast and with a lot of force. Well, that top hinge and actually detached from the door..and it swang quite fast...into my forehead.
Well, we had quite a laugh about that. That is, after i stopped seeing stars. Now i have a bruise on my eyebrow. I'm just glad it didn't smash my glasses.
But i will be cautious the next time a dude opens the door for me.