I expect failure will not be so much whether you make the right decisions, but whether you have a loyal team or whatever they do in Mass Effect 3. Remember in Mass Effect 2 it was possible to die, but only if you let practically everyone in your team die along the way. And that meant keeping everyone non-loyal, not upgrading your ship, and making a few bad decisions.
Who should hack the door? Grunt!
Somehow, I get the feeling that if I go out of the way to get the bad ending, I'll hate it and it'll piss me off. It'll be a long extended scene as the Reapers destroy, pillage, and kill the galaxy. So, I'll probably hate watching them win. And that's how it should be.