Not failproof

If I can search for any friend with whom she has recently interacted, I am a few clicks from her. If she posts anything to public pages (say, the page for a TV show or music band) I will have a direct link to her profile. If she joins her school's page, everyone in the same school page is one click from her profile - and school affiliations are not verified so literally anyone can join. So, while "hidden from search" is a setting that I would recommend to any paranoid parents (and to many adults without molestation / sexual harassment / stalking worries too, for other reasons); it is not as strong as it looks at first sight.

Heh, I have been studying socnets (and joining several) since they were still rather marginal. I never predicted they would take off so fast [which explains why I don't have that many tween girl friends], but it didn't surprize me that they did.