I've always wanted to, because I had heard it was better for my back, but as far back as I can remember, I've slept on my stomach, which I've been told is the worst thing for my back.
I have had large breasts about half as long as I've been alive, so sleeping on my stomach requires some effort. I prop my pillow on top of my forearms, which forces my elbows to stiffen in an "L" shape and causes my shoulders to arch up, as though I am carrying a stack of books. This is all in an effort to make my boobs less smooshed.
Often I will wake up and both of my arms are asleep, leaving me to gimp about the apartment, unable to grasp anything until blood circulation returns. It is pretty stupid, but it's the only thing I know to do. Either that or double up on pillows. It's bad on my back but I've gotten used to it.
It amazes me how easily we grow accustomed to things that are bad for us.