Underage users

Can someone explain to me why Youtube/Facebook/MySpace/Bebo/etc allow a child of the age of 11 years old to create an account on their sites without even attempting to verify their age?

I realise it states to put in a DOB, but most of these kids put in a fake one. Why not FORCE verification on the user by way of credit card, etc. If a kid wants an account their parents require a c/card to be verified.

>>10
Unlike Australia, the US (where 4chan's servers are located) has a First Amendment stipulation in its Constitution which states that Congress shall make no law abridging freedom of speech, press, etc. So I doubt a censorship plan would get far being that everyone from the most hardcore conservative to the most liberal progressive would be up in arms about it.

We need age verification here STAT!!!
No, no, and no. There won't even be a CAPTCHA, so forget about age verification.