*remembers* ah Pong, PacMan and Lunar Lander how I miss you all.
I'd be inclined to say that 'online' age differs greatly from 'real' age. I'd say your true age is at least 75% determined by how you manage to behave online (and offline for that matter).
One of the main reasons why I rarely give out my 'real' age is because it tends to 'fudge' how people think of you. People will approach you completely differently when your age says 40 instead of 14 when in fact a 40 year old can behave like a 14 year old and vice versa.
People have a tendency to reveal their 'true' age after only a few posts here and there anyway so I hardly ever look at the age indicator.
I guess if time is relative, age must be as well hehe