Assuming people have the balls to actually cancel their pre-order and not buy the game. There are a lot of people who bitch and moan about game companies decision's concerning their games, but very rarely do these people seem to do the most effective thing to tell the game company that they don't like it, which is to NOT BUY THE GAME. Its like the people who complain about securROM yet who still buy the game and just send a letter(or so they claim) to the company. They don't give a shit about any of that letter crap, once they have your money they could care less, and if you continue to buy their games you're just perpetuating the problem. Vote with your wallets people.
It's actually worse than that. A lot of people will end up pirating the game and make it clear on forums or whatever that they pirated the game as their way of "protesting". But all that does is two things:
* It shows that those complaining can't really be that serious as they aren't prepared to do without, which makes one's position much less credible, and
* It gives publishers another data point when talking about game piracy numbers.
If you really truly have an issue with a particular software company, and you feel that the only way to make an impact is to not give them any money, then you also have to accept the fact that making a credible stance HAS to also include not using their software, even for free. Otherwise, you're part of the problem.
Having said all that, sticking to these principles can be rather difficult. Particularly when one is young and was brought up on having tons of pirated content on their hard drives. :)