I don't go around telling everyone about it, but it's more because that's boring. I know from experience (i.e. listening to others) that people constantly telling everyone who will listen about there hobbies, whatever they may be, soon labels them a bore!
However being 31, people just see it as fun and a little eccentric. I think the tough age is late teens, when you 'should have grown out of such childish things'. When you get older you are somehow allowed to fall back as long as the rest of your life is adult and in order I guess!
Everyone should have a hobby, I have LEGO and now photography.
Pleanty to do, both far to expensive though ;-)