Bang Bang, On the Door Baby

So in my current living situation I am in a college dorm. Yes, here I am a 27-year old male and still living in a dorm. You have all the rights to make fun of me. The setup is where each pair of rooms shares a bathroom. Most of the time this is not a problem. You go in, turn on the light, do your business, and be gone. There is a gap between the bottom of the door and the floor so seeing the light on is a dead giveaway that someone is in there. Even if, a slight knock is polite just to check. Well apparantely my suitemates don't think like this. There have been several times in the recent past that I am sitting there, taking care of business while enjoying an article in SI that the one of the suitemates (there are 2 brothers next door) fails to knock and just opens the door. I really don't get this. I mean, how hard is it to 1) look for the light and 2) knock. After the most recent episode, I decided to take longer then necessary just to spite them. I have also gotten to turning on the faucet and letting it run so there is an audio cue that someone is in there. At this point, who is it more embarassing for -- me who is just sitting there or the neighbor who continually makes this mistake? Then this morning I was brushing my teeth. I like to multi-taks and walk around when I brush. I was in my room and I heard them open the door. Geez! Can't you wait until you see the light off? And speaking of lights, the neighbors, for whatever reason, like to leave the light on in the bathroom even when they are not in there so I knock regardless to make sure the facilities are empty.