Oh, the things that interest me. Thanks for being so endearing. I've always been interested in which side of the bed someone sleeps on.
For the sake of consistentcy, in the picture, the man is on the left side of the bed.

I have a whole bunch of theories why folks sleep on which side of the bed. My theories are probably wrong. Besides answering the poll, I'd like to know:
1. If you know why or what factors cause you to sleep on a particular side of the bed.
2. Have you ever changed sides of the bed willingingly/unwillingly?
3. If the side of the bed doesn't matter to you, I'd like to know why too.
4. Not that you folks need the encouragement, but feel free to add anything else.

1. the other's choice
2. 1st wife 2, this one 4.
3. ah, 'cause I don't care OR left handed, semi-ambidextrous?

I want to know why she's wearing her gold watch to bed. "Yes, dear, that took exactly 45 seconds."

I sleep in the middle of my bed!

Not sure why but I sleep on the side furthest away from the bedroom door. The house I am in now it's the left side. Yep, I have lived in five houses and this is true with each one....interesting. Never thought about it before.
Maybe if there is a break in my sig other gets it first?.....

My wife doesn't pay near as much attention to left and right as I do. She always thought her side of the bed was the side by the window and in most of the places that we've slept, that was true. The first time we slept in a bed where the window was on my side of the bed, I could not convince her otherwise, so I told her to get into bed. Only once she was in the bed did she realize what was going on. I love her.

Very smart move sleeping furthest from the door if you're expecting an attack. Not so much if you need a quick exit.

1. spouses choice
2. yes - changes have happened when we moved but not always
3. ?? - don't think it matters ... but see 4!
4. Now that I think about it our bed has usually been E-W and I sleep on south side (whether that is left or right - but it has usually been right, head of bed -> East)

Single, so wherever the h*ll I want to!
(but mostly in the middle where I can hog it all)

I'm about as tall as my bed is long, so when you add in the space the pillow takes up my feet tend to hang off the end a bit. My solution is to sometimes sleep across the diagonal of the bed and sometimes curl up a bit. I switch between sleeping on my stomach and sleeping on my side and I switch which side I sleep on as well. Sometimes I like having my back against the wall. Sometimes I like being so close to the edge that I almost fall off. Sometimes I manage to end up almost exactly in the center. There are no real certainties in my sleeping habits except that I don't sleep on my back. Unless I'm sick.

I have a whole bed, so I tend to move toward the middle, but favor the right side, as the right was my side for years of sharing. In my current configuration this is unlikely to change, because I've got a lamp, clock, books, etc on the right.

However, in earlier days, with a different room config, I had the left side because it was nearest the door, and I was most apt to be the one to wake at the slightest baby squawl and attend to that sort of thing. This is not to say that I didn't, at times, shake my husband and make him go get a kid for me.

See, this is one of the things that interests me. Why would two people mid-relationship switch sides of the beds? We gave that a go once. I remember the discussion. After about 2 minutes, we both couldn't take it anymore.

Our assigned bed spaces are the opposite of our assigned car seating.

1. If you know why or what factors cause you to sleep on a particular side of the bed.
mostly, if I've reaching out to embrace my partner, or to pick fluff out of her hair or biscuit crumbs off her face, I'd prefer to do that with my dominant hand, the right.
2. Have you ever changed sides of the bed willingingly/unwillingly?
Yep, to see if it made much difference. It didn't. We went back to our regular disposition.
3. If the side of the bed doesn't matter to you, I'd like to know why too.
I'm asleep. Or doing something else.
4. Not that you folks need the encouragement, but feel free to add anything else.
Of the few sleeping partners I have enjoyed, I have always been on the left hand side of the bed. I can't recall if any of my partners were left-handed, but that might have made a difference. At least, to them.

I sleep all over the bed and the floor, my wife has a keen sixth sense about when she needs to move, quickly.

In general I'd agree with you Mutey...it's weird to switch sides. But if you are in a different room--guest, hotel, etc, sometimes it works to switch. I guess various types of caregiving--attending to kids, or facilitating helping an adult get to the bathroom more easily--have made me flexible. So, if we were at the beach house, eg, and the porta-crib most easily fit on the left side of the bed, I'd take that spot.

IB--your handedness theory only works if the two parties have different dominant hands. Oh, I see you observed that.

I am right-handed and sleep on the left side of the bed. My wife is right-handed and sleeps on the right side. In hotel rooms we sometimes switch sides but usually not.