I personally think these groups do need to exist. Banning them won't cure people of anorexia and at keast they have others to talk to who understand how they feel - something no non-anorexic can.
There again, others may say that these social networks will encourage young people to over-slim and eventually get anorexia. That also may be a valid point. But I still don't think banning them is the answer.
What do others think?

I agree with you... We all look for affinities... Why descriminate... Besides driving any group underground just means removing the problem temporarily... If we don't see them it doesn't mean they don't exist anymore....
If they join in the social network, it probably means they're coming out of their shells and looking around and in need to comunicate with the world and who knows they may find their way back to health....