My son has in my view benefitted from Facebook, as he has been able to have interactions with his peers in a way he never does face to face (he has Aspergers) I am writing an article about this, and would be interested to hear from (and maybe interview) other parents of Asperger children to get their perspective. Please contact me if you would like to chat about this
I have a friend with Aspergers and for a while she drove me along with everyone else on FB crazy with her status updates and I must admit that I have actually "hidden" her updates as consequence.
She would say how stupid she was for not getting things, or how fat and ugly she was as she is trying to lose weight - and other similarly depressing updates that made us all very concerned about her and also made us (angry?) because no matter how much help we gave her, she still continued to tell the world these awful things about herself that were really inappropriate for a status update.
She has also fallen out with a few other people that she has met via Facebook/other virtual places who also have Aspergers as they clashed writing things as you cannot tell tone from text alone.
I think that it is good that you can meet other people through Facebook - but sometimes, it is good to know that just because you have the same condition does not mean that you have to be friends - or that you'll have things in common outside of your condition.
She's also had problems with spam mail as she doesn't grasp that people lie and that they aren't telling the truth.