I'm curious about that checkbox. The whole reason for it, I'm guessing, is because of COPPA ( Children's Online Privacy Protection Act), but then that applies only when you collect a significant amount of personal information from someone 13 or younger and/or directing them to behave a certain way.

Which leads the question, why would Quora need that much information about me in the first place? I don't recall getting an "I'm over 13" checkbox when I signed up for HN and we're ostensibly doing the same thing: Discussing.

The same is true for most sites, even Stack Exchange, because of COPPA as mentioned below. If you mention openly anywhere that you're below 13, moderators are obliged to delete your account (since they can't keep your personal information)

> Subscriber certifies to Stack Exchange that Subscriber is an individual (i.e., not a corporate entity) at least 13 years of age. No one under the age of 13 may provide any personal information to or on Stack Exchange (including, for example, a name, address, telephone number or email address).

- http://stackexchange.com/legal