Many of years ago I worked for a start up company that was building an 'Executive Work Station'. Yes ancient times to most of you. The company failed, but I was working with people whom to this day I think were the smartest people I have known in IT. That being said, it still failed. The key to the failure was the founder who on more than one occasion said: 'I do not know what I want, but I will know it when I see it'
Needless to say this is had to develop to. In the end it doomed the company.
I learned: for a project / company to succeed, someone has to have a clear vision of where it is going, and thus know when you are there.
What lessons have you learned from failures?