I will give you a personal anecdote of my company. We failed (not ending in bankruptcy thankfully) because 9/11 caused all our customers to freeze and not be able to make a decision. We end up in the situation where everyone said yes on an intellectual level, but they just couldn’t sign on an emotional level because they were too uncertain about the future. A year later they were over this, but it was too late.
I'm looking for some stupid things that were made by the management team that caused startup to die.
More seriously the real failures I have personally seen have never had a single cause. All the ones I know of are a combination of a lack of resources (money can buy you out of a lot of mistakes) and inexperience.
There is a documentary about them also: http://www.imdb.com/title/tt0427783/
The idea was to give away cat-shaped barcode scanners to make it easier to scan URL's. $185M down the drain.
16,000$ for a fat-ass phone