Before someone borrowed the term 'canon' in relation to Star Trek, it used to be referred to as 'continuity'. It is the concept that there is a consistency in the integrity of the continuing aspects of any series, not just Star Trek. In fact, I prefer the term 'continuity' over 'canon' for something like series television or series movies.
The point of continuity (or canon) is that it helps establish the show and the truth of the characters and the themes and the details for the long term viewers. The casual viewer may not care where Anakin was born (for example), but a watcher of all the Star Wars movies would object if, after having established his home planet as Tatooine, his home was later described as being Delaware.
Likewise for Star Trek, continuity establishes details of the technology, the back stories of the principle characters, and the histories of the episodes that have been made. If one episode shows Spock to be a vegetarian, then it isn't good for a later episode to show him sitting down with relish to a juicy sirloin steak (unless there is a justifiable story point, like Spock is possessed by an alien entity who likes sirloin). A change of this order would immediately strike the viewer who knows better as being a major error.
I hope it is plain that continuity, or canon, is the friend of good story telling, and not the enemy. If adhered to, it forces writers to write better stories than if they just take short cuts to make an exciting scene by throwing continuity out of the window.
Perhaps contrary to appearances, most people who support continuity don't get bent out of shape about really minor errors, but merely point them out for interest's sake. There is a concern in the minds of some that JJA's movie won't contain merely small violations of continuity, but whopping big ones. This isn't proven yet, but it is a fear.
If the details of the story depart too much from what has gone before, it will not be reconcilable with what is already known, which does violence to the overarching Star Trek story, especially as this movie is a prequel and therefore sets the stage for all the Trek that comes afterwards.
I hope this helps.
If you are too open minded your brains will fall out.
Last edited by Bright Eyes : 12-02-2008 at 12:31 AM.