Can't you like... alter your MSN settings so that you have to approve of people before they can talk to you? That way, you can screen if you think it's a friend or the freak again. Whenever someone has tried to add you, you get this pop up window when you sign in, asking if you want to allow this person to see if you're online etc.
Hope that helps at least a little
Poor Sarah :/
Damn slow typing
What he said.
Well.. either what he said, or Tools - Options - Privacy, and check 'alert me when other people add me to their contact list'