Timwi stated for the record:
I am wondering to what extent COPPA applies to
Wikipedia, and
whether there is any legal risk for Wikimedia if American children
under 13 years of age use Wikipedia without their parents' consent?
It does not apply at all. COPPA specifies what information a site is
allowed to collect about children under 13. We don't collect any
applicable information about our users.
How does the law define "collect"? We do store all information that
these children put on their user pages themselves, in the same way
LiveJournal stores only information that was entered by the user...