It is possible (not fixed yet) to steal Skype account, knowing only Email of a victim! No need an access to mailbox. Skype allows to register several accounts for the same email without sending a confirmation link. As result, someone who knows your email, can register skype account for your email and steal your Skype account.
The problem is not fixed yet and known only in russian internet at the moment...
The only way to avoid this at the meoment is set a such primary email address, which nobody knows. I've maid an alias for hotmail account with GUID as a email.