When I first started playing STO, I thought the game might be canon, because it sticks very close to other canon sources, but as I have played farther into it, I have found quite a few non-canon references. So, would I be correct in assuming that STO is not canon? I know it's a stupid question, but I just want to be sure I guess.
it follows what you seen happen in all the series, ST: TMP through Nemesis, and the start of the new star trek movie, up until spock and nero go back in time.
since STO is considered "soft canon" they have SOME liberties with what they can do with the game, but anything major they want to add/change would have to get oked by CBS first, an example of this was that The nebula was originally going to be a cruiser, but CBS didnt like how they did it, so it had to be reworked and resubmitted for approval.
From what I have heard the game is soft-canon on the level with the books and comic books. Almost everything that goes in has to be approved by CBS (the current IP holders). Hard canon is the TV shows and movies.
So STO is considered canon unless something in a TV show or movie comes out to contradict it. In which case the TV show or movie takes presidence.
In a similar vein, books in the Trek universe are usually soft-canon as well. Thus as long as they do not contradict what happens in a movie or TV show, are also canon. Thus we can see characters and events that happened in various books also appearing in STO. A good example is MacKenzie Calhoun from the New Frontier books who appears at K-7.
This game is canon just like the current storyline for the books. It is just that they are in different realities. If a new Star Trek movie or series is created that contradicts the other storylines, then it will be the main reality.