Lord Vader wrote:

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Success in multi-player will have a direct impact on the outcome of the single player campaign
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Man, I've been watching people scream about that for over an hour.
Note that it has only optional bearing on achieving things in the main game. That's a very important issue right there. It can help or it can be completely ignored and that perfect ending can be found without booting it up even just once.
Chris Priestly was very careful to point this out, even going so far as to comment that he himself is all about the single-player, insinuating he may ignore it.