This is a prime example of a show that has completely lost its way. The writers seem to have forgotten the 70 or so unfinished story threads that are already hanging out there and have now decided to stray off into an unexplainable time-travel story arc.
I am a huge fan of science fiction. I have seen more films and read more novels than most. No one is more excited and intrigued than I am when an unusual or unique story sees the light of day and "Lost" definitely qualified when the first season rolled out. However, it became painfully apparent that by the end of the third season, no one involved in the production of this show had any clue as to where this story was going anymore. What was an intriguing tale of the mystery of this island and the star-crossed destinies of the Oceanic 815 survivors has deteriorated into a "What-other-weird-crap-can-we-throw-out-there"-fest.
This sad excuse for an episode is just another example of that.