Can an island really move like the island(s) on Lost? Short answer yes. Maybe not through a donkey wheel in the bottom of a well, but an island can definitely move around.
The not so technical term is a “floating island” or tussocks, floatons, or sudds. They form when vegetation grows out from shore and eventually becomes buoyant and the roots can’t grab hold of the ground. A heavy wind can shear it off and set it adrift. They’re actually fairly common in lakes. Some are as large as a football field (or more) and can have trees and animal life.
Going bigger, are pumice rafts that can be created in a volcanic eruption. One raft formed by eruptions around Tonga near Fiji was 30 miles wide. That’s more than enough room for the passengers of flight 815, Jacob’s cabin and a few polar bears.
Prior to plate tectonics theory it was the popular scientific belief that life spread from continent to continent via very large islands formed from either from vegetation or volcanic activity. This theory may still explain the spread of some species post tectonics and ice ages.
Satellite imagery has taken some of the mystery out of finding these strange islands, but history is filled with interesting anecdotes and myths that may be based on truth. The island of Avalon from Arthurian legend may have been an actual place based on one of these floating islands. Numerous sea expeditions charted islands that were never located again.
So not only is a moving island a possibility, it’s a reality. The good news is you don’t have to crash land in the Pacific to find one much less spend a 3rd season going through pointless flashbacks. Here are a couple that are on the charts:
The Uros people and their (artificial) floating islands: http://en.wikipedia.org/wiki/Uros
Island Pond Island in Springfield, Mass: Drifting into Debate