It's kind of funny reading these comments. In my area, we can expect to be carded even if we look 40. It's just natural not to go anywhere without a valid ID, and have it ready when they ask.
I don't get offended when I get carded for alcohol, but I really hate it when they card me for smokes. I look very young for a 34-year-old (clean-shaven, short hair, etc. -- see Rogue's), so I guess I can expect it. But when they don't card the person in front of me who appears 25 but is really 16 because he's an overweight slob with full facial growth, that tends to tick me off.