There were times where it didn't. Especially when I unlocked it... talked on phone and let it go idle. I could see the smudge later. Not saying it would always be there, but often, it was.
I agree that the Droid needs a number locking system. I just upgraded from a Blackberry and loved that locking feature. Hopefully they will impliment that on the Droid soon.
In addition to pattern lock you can also add a credential storage password
Menu > Settings > Location and Security
scroll to the bottom of the screen and set an additional password
I be;eive once this is set you cannoy remove password uless you clear all credentials and password