I have a feeling that maybe the unwanted friends is a WGT bug rather than a hacking attempt. I'm guessing that it happens sometimes when somebody sends you a friend invite and somehow it gets auto-accepted (due to the bug) rather than you seeing it in your Invites and then having the option to accept or decline.
It's also obviously a bug when you remove someone from your Friends list but they still appear on your Friends list and / or your friends count. I've had that happen before, too. Recently I removed 3 players from my Friends list, on Flash, but my friends count has not gone down, and if I go to each player's profile page, the "Remove Friend" button is still there.