Why do software projects fail? : Santomania, Redux

Why do software projects fail?

Nothing has to go spectacularly wrong for a project to fail. Projects fail by default when they are big and/or complex enough. Be paranoid, and very very afraid :) Or, in more concrete terms- If your project plan doesn't have mitigations for the expected risks baked in from the start, how the heck do you expect to deal with the unexpected ones?
Complexity kills. Teams which don't constantly strive for simplicity are doomed from the start . Agile methodologies are but one aspect of the quest for simplicity.

Complexity & overhead increases non-linearly with team size, so always strive for the smallest and smartest team you can put together. Bigger is worse, and a single qualified developer is always better than any number of monkeys.