Accountability is a key element in any arena. It's a popular word to use in politics these days, but so often, it's as meaningless to the Bush administration as it is to many companies. Most people will take personal responsibility, and take accountability as a point of honor. When this happens, usually there isn't much of a problem. When it doesn't happen, there needs to be something to make accountability meaningful.
The obvious answers are often simply "negative reinforcement". You're fired. You don't get your bonus this year. You don't get the promotion, or you get demoted. You are removed from the project. Of course, the punishment should fit the crime. If someone misses a deadline for the first time in their five years with the company, firing them is probably not worthwhile. If someone misses twenty deadlines in a row, in their first two months, they need to be kicked to the curb.
The most important element of accountability, though, is follow-through. At Hotelecom, we actually had a fairly good plan for holding the engineer accountable; the problem was, we never did. We laid out a plan for what to do when he failed to deliver, and then proceeded to ignore it. We extended the deadlines again and again. After letting him "off the hook" several times, was he truly accountable? Perhaps the failure was holding management accountable for actually managing the project, and their failure to pull the plug as planned. What happened to them? Nothing, really. After all, they were management.
Which brings me back to the topic of leadership -- the upper levels of management must hold themselves accountable, because there're so few people above them to enforce it. Management should lead by example, ensuring they themselves at least make all possible effort to make deadlines, make plans to fall back on if things don't go according to plan, and stick to their guns. When plans don't change, but situations do, it should be made clear to everyone why you haven't changed course. It's perfectly acceptable to say that the backup plan, given recent developments, would not be viable, so there's no choice left but to continue on with the original plan. However, this has to be communicated, otherwise the impression that you are simply ignoring your own accountability, and people will feel they should similarly not be held accountable (or they'll feel they're being unfairly treated if they are held strongly accountable, but management is not).