“Lost” is, in some sense, in the dark business of exploring just how futile the modern search for peace, knowledge, recovery or profit really is. The failure of people to combat their most debilitating weaknesses is one of the show’s most compelling themes. In the recent flash-forwards to the survivors’ post-marooned lives, we see Jack drinking; his girlfriend, Kate, living a lie; Hurley lost to bizarre superstition. At the same time, Sayid, a former member of the Iraqi Republican Guard, is avenging his wife’s death as a killer for hire and, so we must assume, failing to find redemption. (source)
But it doesn't collapse into nihilism--on the contrary, actions in the world of "Lost" have moral weight and meaning. In fact, the show's fascination with meaning and consequence is what drives the drama.
There is a theology undergirding "Lost" that deserves some Christian critique. Redemption does happen on the island, but it is usually earned rather than a gift of free grace. Yet this world is highly providential ("fate" comes up a lot) and one gets the sense that the characters are being constantly challenged to grow beyond themselves.
One of these days I should search the Web for sermons about "Lost"--I'm sure there's more than a few out there.