In a few months we will get to see the eighth Star Trek movie, and the rumours abound that we will finally get to discover the dark secret of the Borg. Unfortunately I don't expect Paramount to have a terribly good secret for the Borg after the debacle that was Generations. However the premise does lead to interesting musings.
To begin let us review the Borg. We know they are a collective conciousness who roam the galaxy, assimilating cultures into their culture. They are on an, almost holy, crusade to 'improve quality of life for all'  and seem genuinely puzzled at resistance to their efforts. They demonstrate strong technical expertise and are technologically the superior of their immediate rivals. Their calm, methodical, spread through the galaxy has been, and is, cause for alarm for the parties not yet a part of their Culture.
But doesn't this sound awfully familiar? Replace the word Borg with the word Federation and you have a fairly accurate assessment of the Federation and it's effects on the Galaxy. Certainly the Federation would be unlikely to admit to being so similar to the Borg but the paralells are quite striking. Like the Borg the Federation believes itself to be on a quest to improve the quality of life for all. Indeed it's own expansion through the galaxy has been cause for alarm for a while with the local residents of Alpha Quadrant.
Of course the fact that the Federation is expansionistic is not neccessarily the important reason they are like the Borg. No rather it is their zeal to incorporate everyone they meet, even enemies, into their collective Culture. Naturally the Federation claim that their prime directive and general attitude of non-interference mean that Cultures in the Federation are not adversely affected.
Yet how many times have we seen the Prime Directive broken by Federation personnel? Certainly some of the incidents can be fairly described as accidents but by ignoring that possibility of accidental interference the Federation tries to paint an overly positive picture of their effects on member cultures. And to even ignore the blatant direct interferring in member politics that the Federation indulges in you come to the simple point that any exchange of information and trade between cultures is invariably going to end up affecting both Cultures.
The Federations policies of personal freedom, fair government and other such 'human' rights can not help but have a trickle down effect on member states in the league. It is a strong and somewhat xeno-phobic culture indeed that can resist such cultural change. To become a member of the Federation is to implicitly sign away a portion of your cultures future heritage and decision making abilities as cross-cultural polination infuses previously unthought of ideas and norms into your culture.
Now by no means is this always such a bad thing, and often the synergy between the two cultures as they interact and change can be extremely beneficial. However I raise it specifically to point out that the difference between the Federation and the Borg is largely a matter of degree. If anything the Borg are far more honest in their goals and aims, stating it quite bluntly as they continue their crusade to improve the galaxy. They are here to assimilate your culture, it's technology and by neccessity it's art and ideals as they are so often tightly tied with technology.
Naturally in the exchange you surrender much as well. But consider this, while the Borg's collective thinking and seeming indifference to individuality seems abhorrent to the Federation I contend that again the two are merely different by degree. Through active intervention, sending starships & the like, and more passive means, trade & cultural pressure etc..., the Federation is actively engaged in changing the thinking of it's members as well. The Borg's methods are merely more direct, more personal and considerably quicker.  Secondly for all the Borg's apparent indifference to individuality they do not actually strip it away. Each member of the collective exercises an influence in the decision making process, is aware of itself as an individual as a part of a greater whole  and in general the collective acts in a fashion similar to logical extreme of democracy with every member having a say in every decision.
So, if you agree with me thus far, the Borg merely seem to be the logical escalation of the Federation's policies then it leads to an interesting question. What if the Borg are the Federation, displaced back from future events through some form of temporal anomaly? Sufficiently far removed from their origins that that information has been either forgotten or lost to the Borg and they now are persecuting a war against themselves and threatening to create a paradox in the timeline.
Could this be their big dark secret?
If it is then it has some important ramifications, most important of all - they will lose the fight with the Federation. Every time we have seen time travel used in the Star Trek universe there has always been one common factor, a core set of people in a position to avert drastic changes in the timeline.  And despite the odds these people invariably succeed in restoring the timeline, even when the rational and measured odds indicate that their efforts are almost certainly doomed. The universe itself almost seems in collaboration here, ensuring that the one true timeline can always proceed.
Accordingly I would like to propose the Temporal Censor Theory. This states that every universe will have one, and only one, timeline. Any attempt to alter the timeline will be actively resisted by the universe and the original timeline will be restored. As part of that resistance the universe is empowered to ensure that the right people & resources are emplaced to correct any breach of the timeline.
Suddenly the adventures of the Enterprise and her crew become
entirely sensible. They are merely the currently chosen agents for
enforcing the timeline and correcting any attempted breach. All the
improbable escapes, the convenient availability of neccesary resources
for saving their skins and the inability of overwhelming forces to
destroy the Enterprise is explainable. As Commander Riker notes 'Fate
protects fools, children and ships named Enterprise'.
 Locutus - 'Best of Both Worlds
 I reference the speed and ease with
which Captain Picard was subsumed into the Borg collective to become a
highly productive member of the Borg in a very short amount of time.
'Best of Both Worlds Part 1'
 In 'I, Borg' the captured Borg
reports itself as '1 of 5' where by, given the number of bodies and the
small size of the Borg scoutship, it can be reasoned that five was the
crew compliment of the ship. The Borg was indentifying itself as an
individual member of the scout crew.
Note also then even after induction into the Borg Captain Picard
still was referred to as individual, merely the name changed to become
that of Locutus.
 See 'Yesterdays Enterprise',
'Time Squared', 'Times Arrow', 'City on the Edge of
Forever', 'Tomorrow is Yesterday' and various other episodes
as examples of this.
Philip R. Banks
 Locutus - 'Best of Both Worlds Part II'
 I reference the speed and ease with which Captain Picard was subsumed into the Borg collective to become a highly productive member of the Borg in a very short amount of time. 'Best of Both Worlds Part 1'
 In 'I, Borg' the captured Borg reports itself as '1 of 5' where by, given the number of bodies and the small size of the Borg scoutship, it can be reasoned that five was the crew compliment of the ship. The Borg was indentifying itself as an individual member of the scout crew.
Note also then even after induction into the Borg Captain Picard still was referred to as individual, merely the name changed to become that of Locutus.
 See 'Yesterdays Enterprise', 'Time Squared', 'Times Arrow', 'City on the Edge of Forever', 'Tomorrow is Yesterday' and various other episodes as examples of this.