Right handed, male, left side as per OP’s definition i.e. seen from the foot (but I think of it as the bed’s right-hand side because, lying down on my back, I am definitely on the right). The main reason is that it’s her bed so she staked out her territory first, but it’s also more practical to use one’s dominant arm for interpersonal haptics.
We mostly chose the same sides when traveling btw.
Honey? I sleep furthest from the door so that if someone comes in to kill both of us, I have a chance to escape while he is finishing off my husband. In fact, if we sleep in a different locale, I switch to whichever side is furthest from the door.
My bf prefers to be on the side furthest from the door. He claims that’s so he can see the door and spoon me. We both quietly know it’s that I get sacrificed to the monsters first.
I’m a righty and sleep on the right. She’s a lefty and sleeps on the left (obviously). This means that during sexyfuntimes, we each use our non-dominant hands on each other. We generally sleep with our backs to each other, but often in the morning I’ll spoon her, and our morning spoonsex occurs on our right sides. We were actually just talking about maybe switching sides just to mix things up a bit and have spoonsex on our left sides, and give our dominant hands a little more action, but it hasn’t happened yet.
I’m not currently with someone, but it was the exact opposite. My ex felt uncomfortable if I wasn’t the one closest to the door so I could defend her if someone broke in or something. Personally, I didn’t care so I just went along because it made her happy. If for some reason I was asleep on the wrong side, she’d wake me up and make me move or if I had reason to be on the wrong side (like when I had an injury that made being on the “wrong” side more comfortable) she’d try to convince me that I didn’t really need to and, well, those situations were was frustrating. Anyway, how this worked out was that it required I sleep on one side at her place and on the other at my place.
I sleep on the side closest to the door. This is consistent, whether we’re at home, traveling, etc.
I sleep on the left side of the bed for a very simple reason: my fiancee likes sleeping on the right side of the bed. I didn’t have an actual preference and she did, so I got the side she didn’t want. I usually sleep facing away, towards the window.
I’m a married straight guy, and I currently sleep on the left side. This is just because my wife likes to be closest to the bathroom.
This has the side benefit that, since the master bathroom is opposite the main door, I am closer to the exit than she. I think a house fire is far more likely than an axe murderer, so I’m in good shape. If the fire alarm ever screams in the middle of the night, I’ll be first out of the door and on my way to safety. Sorry, hon, you picked the side.
Right handed. When sleeping alone, I sleep on the side where the clock is.
When sleeping with a girl, I prefer the side closest to the door. I read something a long time ago that men “instinctively” do this as a protective actoin, and it has infected my brain. I have to sleep on the side where the exit door is. And no, it’s not so I can slink off without waking her up. 
Right side, as you look from the foot of the bed to the head.
But it’s changed a couple of times over the years. My wife will just take over the other side of the bed from time to time - because her breathing or comfort change.
When I was married I slept on the right side of the bed. Mostly because if I’m going to sleep on my side, it’s my left side and I’d prefer not to get a mouthful of hair or be breathing in all the air she’s breathing out. Everything just gets to warm that way. I didn’t really happen on purpose though. It started because when we first started living together the right side was closer to the door and I went to bed after she was asleep. It was easier for me then walking around the bed in the middle of the night.
Right handed, right side of the bed (as I lay on the bed at least).
My wife has switched with me a few times, usually whenever we move to a new place she takes over the side closest to the bedroom door. She gets up much more quickly each morning, so that way she doesn’t have to crawl over me to start getting ready.
I sleep on the right, because I have no preference but my wife claims she can only sleep on the left side. My side is also the side nearest the door, but I don’t know if that has any relevance.
I’m right handed, and I sleep on the right hand side of the bed.
What I assume will be the problem with this poll is that 1) Far and away most people are right handed, and 2) Since you’re talking about be positioning; both positions are represented. In other words my wife and I are right handed; but we represent both sides of the bed because there are two people for two slots. I think it would have been worth the complexity to add gender.
As an unrelated FYI, my side of the bed is usually chosen by the side closest to the bedroom door.
Left side, right handed. In our old place, I was on the right side, but I prefer the side closer to the window, whichever that is. My husband seems to prefer the side closest to the door, so it’s worked out well so far.
I’m not cohabiting with anyone, but with guys I date, I take the outside of the bed. The handedness of it doesn’t matter, but if the bed is against the wall I don’t want to be against the wall, and the men I’ve slept in the same bed with are willing to appease me.
My BF and I have a bed that is pushed into the corner of the room, so you can only get in and out of it from one side (or from the foot of the bed). I used to sleep on the left side (the one up against the wall), but we have switched sides in the last few weeks. Sometimes I like switching it up, but most of the time it has to do with who has to wake up first. Since we both wake up for work at the same time these days, it really doesn’t matter… but if I have to wake up first, I want to sleep on the right side so I can slip out of bed without crawling over him.
Male, straight, married, right-handed. I sleep on the right for no particular reason; at our old apartment I was on the left. In general I end up closer to the window; the Ms. gets cold easily. We usually sleep facing apart, but that’s largely because I like laying on my right side more.
It depends on who I’m sharing the bed with, whose bed it is, and sometimes varies night to night. But right more often than left. Even sleeping alone it varies from bed to bed.
I’m right handed.
A couple of weeks ago I stayed alone in a hotel with a king size bed. I didn’t use more than 30% of it. I guess I’m the kind of guy who likes to live on the edge.
Right handed male, sleep on left side of the bed.
It started out in our first house, the door was on the left side of the bed so I got stuck with the “ax murderer/first victim” side. Our current house the door is at the foot of the bed so it doesn’t matter. We just never changed sides.
We used to go to sleep spooning but now we sleep back to back. She has a snoring problem. Well… I snore and she has a problem with it. ( my snoring doesn’t bother me a bit)