Can you give me a few examples of a time when you made a tough decision and it backfired?

One time I had to decide whether or not to get a few in-house systems engineers to assist on the project, or outsource. The in-house team was not particularly familiar with the technology we were implementing, but they were very familiar with the work environment of course. There was the option to outsource the work to experts, but we felt there would be too much of a ramp up, so we rejected the choice to go with their estimate (which was more expensive). Well, it turned out that the in-house resources were constantly being pulled away by functional managers, extending the time and budget by enough to end up much more expensive than if the outsource team had just come in and done the job from the start.