No -- > They're a necessary evil. Because you can't verify the age of a person on the internet by any means affordable by the companies, most kids lie about their age. I knew of many friends with an Orkut account, who were under 18, though the policies are otherwise. On Facebook, its allowed legally to be under 18. Facebook is a bit harsh when it comes to privacy settings, but that's relevant only for those who care for it.
Its unavoidable:- the only cure for this is to spread awareness about privacy issues. Also there is a problem of people accepting friend requests from people whom they don't even know. They are strangers, may be stalkers !
Feel free to ask again !