Yay! Someone wants to hear my theory!
(BTW - I think Ben's "inside man" is Michael...just a thought I had since I know he is coming back this season)
Anyway, I think that the Desmond storyline is really taking us down a path in which the entire island fluctuates within the time continuum (obviously). And this is fascinating to me as a writer because it means that the flashbacks and now flash-forwards are not, in fact just plot devices but actual events happening to the characters. I always noticed that the characters get this little loopy/glazed look in their eyes either before or after a flashback/forward and I think that is because they are all slightly "unstuck" in time. I think that the plane crash and ultimately the destruction of the hatch created enough explosive energy and radiation to affect them all and that they are literally jumping back and forth in time. Some seem to be more unstuck than others - Desmond but also Locke and Hurley. This also makes room for Charlie's statement "I am dead but I am also here." I think that dead characters are still jumping in and out of time but cannot affect it since it has been stated in a few episodes that a premise of this series is "predestination" - things that are to be cannot be changed.
I have been hatching this theory since the first Desmond episode in season 3 and this last one really firmed it up for me. It also explains why you can hear voices in the background during certain scenes, Jacob asking for "help", the injections that Desmond was taking to ward off "the sickness", why women who are pregnant die (if embryos were to jump back in time, things couldn't be good, right? On the other hand, I was also hatching a theory that Ben actually causes this from his own trauma and his obvious latent psychic abilities) the crazy French woman's shipmates going crazy, why Walt is older, and the weird rabbit experiment done by Dharma. Things on the island eventually become affected and jump through time and, without a constant, can become totally unstuck in time and not be able to return.
Okay, this post has gotten really long. Sorry. Thanks for asking, though.
Melissa
ps - The communications guy was a fun special guest star - did anyone here every watch "Early Edition" with the cat who brings the newspaper from the future? My family used to always watch that show and this actor was one of our favorite characters on it.