I imagine I'd be IDed if I tried to go in a bar or club, but I never have.
I don't get ID'd at the liquor store or any restaurants or anything, though. I didn't start going to the liquor store until I was about 19, and by then they were used to seeing me with my parents and older friends, so maybe they just assumed I was old enough?
I probably would get ID'd if I tried to buy from a gas station or 7/11, maybe I've just been lucky....I did get ID'd trying to buy a lottery ticket for my mom when I was like 16, but have never been asked for ID after I turned 18.