i see both points. they could have added something more to fill some of the gaps, but at the end of the day, i didn't have an issue with any of it. to me, it made perfect sense that Tommy would have someone already on the island, and they did build up the Shelby mole in a couple of episodes. and the way i took it, and this could be completely wrong, was that Billy may not have even been totally aware he was being a mole....but anyway....he was. he got set up, and they resolved that issue.
and i loved the ending. this is by far one of my favorite shows ever.
