Update: I am now naked as I've moved to my bed and sleeping in clothes is for squares. :)
I sleep in clothes.
A lot of American people on here have said they sleep naked, but personally I find it uncomfortable. If the blanket comes off me or doesn't cover me enough, I'm too cold, which would happen every night and wake me up. If I cover myself over too much, I'm too warm, and I have very sensitive skin, so the blanket brushing against me would probably wake me. Clothing de-sensitizes me enough that I can sleep and clothes that aren't overly warm offer a medium option for staying warm if the blanket comes off, but they're not too warm if it stays on. I need them for a good night's sleep.
Besides, if anyone comes to the door, I need to be up, dressed and downstairs before they're gone, and if I was naked it would take me too long to dress.