I get asked to remove them from time to time and wont do it. Because they also want you to remove the sticky goo too. Damaged a frosted glass fixture like that once, won't do it again.
I have also been known to put new ones on when the old one aren't legible, or missing. Any excuse to pull out a label maker really. But I'll go out on service calls for cans and find over-lamped trims where the owner couldn't figure out which trim they had and lamp to use, and out comes the label maker.
"Well - I oughta....." -Jackie Gleason