[timurlenk]

There is a secondary discussion if developers should be accountable for sticking to estimates, and my opinion is that they shouldn't - developers should be accountable for the quality and maintainability of the produced code, documentation and tests, not timelines - that's the job of the PM. A good PM will be able to observe that on average the unit of estimation takes 20% longer or shorter and adjust the project timelines accordingly. Also, if someone is worried about developer productivity, it can always evaluate it in relative terms, i.e. how many tasks generated with the above method does one developer execute vs another developer in the same unit of time.