That may be one of the biggest questions of all. I've read many a theory on all kinds of forums, and one really far out there one is that Mark Wickman is an evil twin or Candle, or has been implanted with a new personality, and has grown his arm back, since the new personality hasan arm.

I'm mum on this little twist of Lost. there are plenty of characters in the show with missing limbs and eyes and what not, so you can assume he lost his arm in the purge, so Candle is the evil twin. I don't know, but it's a really great twist that Locke hasn't even mentioned, and he's the only one who has seen all three videos.