Or rather, for their parents... while sex information etc seems to have a home in the wikipedia, parents might not be thrilled at the idea of Junior reading up on anal penetration, cock rings, and other 'adult' concepts. I know I wouldn't if it was my kids... some things are just not for juvenile eyes, if only because too much information leads to very awkward questions.
The front page should have a note on it in the introduction, saying something like 'While the wikipedia does not condone obscenity, articles may contain adult concepts and language unsuitable for children. Please supervise your children's access.' or whatever...