Seriously irritating.
If you accidentally don't check that "I am over 13 year old" box, there is NO WAY to recover except via Snail Mail.
There is not even an email address where you can say "Hey, I made a mistake. I'm actually 39!"
I suggest you make it easier to recover from that mistake. The identity under which I registered as accidentally under 13 is *still* in limbo and that was months ago. I haven't participated in all that time because I was so monstrously annoyed & didn't feel like creating another id.