Project can fail for any number of reasons, but when you start looking at major delays and extreme cost overruns, three culprits emerge:
1. The Teleport

No one disputes that teleporting is a phenomenal idea. Yet, no one has any idea how to implement it. A lot of failed projects are like this. These sorts of projects often arise when the stakeholders get more excited with the ideas than considering the budgets and feasibility. Resource based forecasting isn’t possible because there’s no precedent and the feasibility of the idea is only understood very late in the execution phase of the project.
Examples: Sydney Opera House, Denver Airport’s Baggage System
2. The Winner’s Curse

A bidding process would seem like a sensible way to find the lowest cost provider for a project. In practice it doesn’t always work that way and the winner’s curse means you may often end up selecting not the cheapest vendor, but the one with the least reliable estimates. They appear cheapest, but only because they haven’t effectively gauged what it will actually cost to do the work. Once they are selected as a vendor, they then have leverage to increase costs and things unravel from there.
Examples: Scottish Parliament, Wembley Stadium
3. The Camel

Just as a camel is a horse designed by committee, so camel projects lack one person in command, and typically have large groups of people calling the shots. All projects have large numbers of requirements, but because of the large number of stakeholders these requirements cannot be scoped down to a level that will enable the project to be completed within expected time and budget:
Examples: Taurus, Eurofighter and FBI’s Virtual Case File
