Actually, I've believed Libby was Dharma or whidmore or whatever, ever since around the time she was killed. the Desmond, Whidmore, and Libby thing congealed for me back then with her giving des the boat.

I had originally thought about him putting des there to make sure he never sees penny again..... but later began thinking that whidmore had des there as a way of finding and getting control of the island.