Looks like someone has found the posts regarding under-13s using FaceBook and decided to report
www.mumsnet.com/Talk/am_i_being_unreasonable/1109156
to the StopBadware.org service. Although the idea is not a bad one, the service is used by Google to 'alert' (like 'scare the hell') people that a site may infect their PC, and does its utmost to stop the user from visiting.
Happened also to a client of mine (photographer with his own site) and lost him some visitors and potential work.