First of all I want to say that I read many of the theories here & I actually hope that mine is NOT the correct one but the more I think about this the more I can't dismiss all the clues that seem to be coming together to paint this theory.
I believe these clues point to the losties being the subjects of some sort of experiment where they are physically incapacitated and their minds are networked together in an alternate reality on the island.
It is known in the series that subjects experiencing alternate realities become physically incapacitated. Daniel Faraday even had a subject who became comatose and is being kept alive via Charles Whitmore. As was seen in Desmond's experience after turning the failsafe key there were 'reminders' that kept pointing him to his "true" reality such as hearing the distinctive beep from the hatch. The 'HO' reference in the Hurley centered episode would be reminiscent of this as Ho would stand for holmium. Holmium has the highest magnetic strength of any element & would thereby be implied as what’s being used in the administration of treatments that initiate the experiment on the losties.
Perhaps the Dharma bunnies (the most famous with the number "8" painted on it) are a metaphor for the losties who are actually being subjected to a holmium based experiment and are networked together in a joint experience. Whether the experience is based on a true reality on a true future, past or present is unknown.
Christian Shephard seems instrumental in playing a part of and possibly administrating the experiment. So far (as I remember) its only him that can draw any of the characters out of the 'network experiment'. As Michael is about to die before the freighter explodes we hear Christen say "Ok Michael its time to go now" As Michael says, "Go? Go where?". Also we see it is Christian Shepard who takes Clair with him and away from the losties 'reality' seemingly able to (according to this "losties are test subjects" theory) revive & bring them into their (supposed) true reality. In the scene at the cabin Christian says he is able to speak on Jacobs behalf. Perhaps Jacob & MIB are scientists or Doctors conducting the experiment; each with his own theory and opinion on what is "supposed to happen" The phrase "that's supposed to happen" or "that's NOT supposed to happen" seems to come up a lot in episodes. The whispers we hear could simply be the staff conferring their opinions & /or m! aking suggestions to the subjects at key points in the experiment.
My theory on the smoke monster is that this is possibly the mechanical means by which the electromagnetic effect is imparted to the test subjects to zap them into the experiment, as well as the method used to revive them back into their "true" reality. (They only see it as a ‘monster’ in their alternate reality) We see the losties "flash" through different time periods as well as those on Ajira Airways "flash" back to the 1970's Dharma - we see in smokey flashes of electricity & a very distinctive flashing in the encounter with Kate & Juliet.
I believe just about every piece of information given in the show is relevant so seeing the 'HO' references in the Hurley episode is reminiscent of the hatch beeps in Desmond’s reality. It was shown that tests did take place when Daniel Faraday subjected the lab rat to a setting of "2.342 with an oscillation of 11" possibly using holmium as the active ingredient. It was shown that the radio room guy on the freighter & Desmond were incapacitated while experiencing their alt realities.
Another support for this theory to me is the constant showing certain characters eyes in the beginning of an episode. Whenever a tv show or movie shows somebody's eye implies to me that they are giving the character's perception, or what’s going on in their mind and not necessarily true reality. A lot of lost episodes start out with somebodies eye & again nothing in lost is just by chance, there’s a reason why so many episodes start this way. Especially in the very first scene of the first episode, the sound effect is as if Jacks consciousness has "flashed" into that reality. The sound is almost the sound of some hi-tech medical device administrating a transporting 'zap'.
Another support for the 'perception' aspect is when the same scene is shown in different character centered episodes and small details are 'off'. For instance Ben could be wearing his watch on his right arm in a Jack centered episode while in a Kate centered episode its on his left arm. In any other series it would probably just be a minor filming error but in a series like Lost it’s a clue and this clue to me says that this reality, while shared, is also subject to interpretation by whomever is experiencing it thereby altering the reality and implying that its not necessarily a concrete reality but a 'manufactured' one. Perhaps the final episode will feature the smoke monster dragging Jack down into the temple and as he descends to the depths his consciousness will 'flash' and we'll see Jacks eye opening to him waking up in bed number 23, across from Hurley waking up in bed 42, next to Kate in number 16 etc. etc.
In the episode where Michael repeatedly tries to kill himself (fist in a car crash then with a gun) he is unable to do so. That would be the result of a 'dream' experience of somebody who is incapacitated and could not physically enact his own suicide.
Also every good experiment has its "variables" & "constants". Desmond possibly being the variable with Jack & the other losties being the constants who are acting out what they are "supposed to be" (or "not supposed to be") doing!
Again, in a multidimensional series like Lost, this theory probably would only be one aspect of the scenario. I truly hope for a historical, philosophical & spiritual, deep meaning and life lesson as the core of the series. The show is "zoomed in" (as well as multi-layered; possibly even multilayered told in reverse). It needs to be "zoomed out" to see the overall picture (forest for the trees type thing) but I still would not be surprised if the losties being the subjects of an experiment played into the overall picture in some form. There are just too many clues to this effect to not overlook it.