I responded to a request to register with 'Linkedin' a while back, but have no real reason to network, since I intend to remain unemployed. However my address book has been accessed, and unintended invitations to join me on 'Linkedin' appear to have been sent to everyone listed. Most of those people are not registered with this site, and several questioning responses have not even heard of Linkedin previously. If I've been hacked, it does seem an odd thing to do.