User blog comment:Bronzey/Allies and enemies in Mass Effect 3/@comment-78.1.150.146-20110218180811

"In any scenario, Bioware will obviously still need to cater to those who haven't played either ME or ME2, or who have alienated/wiped out every potential ally they had. This leads me to believe that the final battle with the Reapers won't actually be decided by these allies - instead, the allies will affect the outcome of the Reaper invasion on the galaxy (simply put, who survives the attack and how much damage is done)."

Not necessarily. Bioware has repeatedly stated that Mass Effect 3 will be the last game of the trilogy, and this will enable them to have radically different outcomes based on player choices in ME1, 2 and 3. I'd find it better if it was actually possible to lose to the Reapers in the end if you managed to make an enemy out of everyone. I mean, why not? If you're making multiple possible outcomes, why not make it possible to lose? All those choices leading to a varying degree of the same thing would suck, imo.