my family doesn't close the door when they go to the bathroom. when i say family, i mean my mom, mostly. i've inhereted this unincognito technique to urination (anything heavier than pee, and i DO close the door). it's a side of myself that few people (none, really) have seen, and it's intensely personal, but i love it, because it reminds me of how free my mom is with all of us, and how open i want to be, should i choose to have kids someday.
bear in mind, it took me a while to appreciate it. when i was younger, and even sometimes today, it's a little embarassing. i've got to make damn sure everyone is fully clothed and/or doors are closed before i bring anyone over to visit. it's standard procedure to yell "Hello!?" when i come in the door with a friend. lisa knows, and she makes sure and yells "Knock knock!" when she comes in. [i yell "knock, knock" back, but that's as a running joke from the time she yelled it first, and i meant to reply "Who's there?" and did it wrong. it's been a slight load on my life, that my mom can't keep her door closed in the bathroom.]
Sam had a big issue with the bathroom. it could have been for any number of reasons.. a diffferent background, 2 siblings, strange parents.. but for whatever reason, he not only always shut the bathroom door.. he also always locked it. it seemed odd to me, because we lived together for 3 years, 2 of which were without roommates other than each other. why on earth would he have to lock the door? i really don't WANT to see him shitting. if he's not in the rest of the apartment (all 3 rooms of it), i'm pretty sure (especially if the door's closed) that i'll be able to discern where he is. it just seemed like a barrier that didn't need to be there, i guess. it made ME self-conscious, and lock the door when i was in there. which was odd, for me.
our bathroom didn't have a lock-mechanism until i was ~14.