I was told once that the airlines decide who to check for ID. In other words, it works kind of like a bar: If they think you're 18 or older, they can ask to see ID. Of course, if you're really 17 and didn't bring any ID (or 14 and don't even have one!), what happens then?
Anyway, most government employee IDs don't show date of birth, but they are valid for boarding a plane (government-issued, photo).
Bruce