When I first heard about premortems, the application was project planning. Before embarking on a project, you'd assume it failed and try to root cause the failu

When I first heard about premortems, the application was project planning. Before embarking on a project, you'd assume it failed and try to root cause the failures. You'd then take action to mitigate these risks (or possibly scrap the project completely if you discovered a fatal flaw, but that would presumably be rare). I've since used them to mitigate risks to high-profile events that you can't really simulate, like major product releases or peak traffic events. In those cases, it's important that you do the premortem at a time where it can make a difference. Ideally there is a time when you are more or less code-complete but still have a few development cycles before the big day where you would be otherwise working on polish work.