I've had several friends, whom I know personally, have their Facebook identity cloned recently.  Same profile picture too.  This means that I received an invitation to accept them as a friend again.  I can remember as soon as I received the very first clone request, several years ago, that it just didn't feel right to me.  So I have never, ever accepted a second friend request without first reaching out to said friend via messaging, email, or even a phone call to verify the request.