4-5 years ago, my friends were always asking me to stop inviting them to facebook, because they were already members. It was funny because I wasn't even a member myself. Yet, somehow they were getting invited by me to join.
Cut to a few years later, I joined facebook only because I wanted to see how well integrated it worked with my palm pre. It integrated really well. A few days into my membership, I got an friend request from a college buddy. There was a shadow profile, but I had figured that he hadn't filled his profile out yet. So I accepted. The next day he told me he said f*ck it and joined on my invitation. So, he wasn't a member and hadn't done a friend request. I felt so stupid for falling for it. My acceptance of his friend request generated an invite to join FB from me. I should have known better. Needless to say, I researched how to delete my account. Funny enough, there's still a shadow profile of me naturally. My buddy, on the other hand, lives on the site. I guess he can blame me once he wakes up from his FB daze.