How do you lay when you sleep? Personally, I have no preference. It's not uncommon for me to wake up on the completely opposite side of the couch (yes, I sleep on a couch) than the side on which I feel asleep. I move around so much that I've been on my back, belly, and body sides about 4,000 times each even before I nod off.
I don't really have a preference, and I generally get really uncomfortable with any position really fast, so I'm all over the place when I sleep. Most people I talk to either feel the most comfortable on their back or on their side, and it seems like there's not many that can stand laying on their stomach. How about you?