Using original Moto Droid, FroYo 2.2.1
Last night, I went to bed around 9:30pm. Read a few pages on Aldiko reader, hit the power button to shut off the screen and went to sleep. My Droid had a full charge.
This morning I woke up around 7:30am and the phone turned itself off, presumably from a dead battery. I hooked it up to the wall charger and after a few minutes (5 or so) it showed a 60% charge.
I thought this was a little unusual. When I went to sleep, the screen was off, but GPS, Sync, and WiFi were 'on'. Screen was set to its darkest setting.