This is what everyone should keep in mind when establishing a start-up. If you have a great idea, don't be afraid to develop it! I think Westbrook's list brings up a lot of good points, which starts by asking, "Is it a new idea?" Well, if you're planning on starting a search-engine website, I'd say you'll never beat Google unless your algorithm is lightyears ahead of Google- which it most likely won't be. The next big aspect is obviously money.
However, the most important aspect for a start-up, in my opinion, is to have a base of customers or supporters to get you started. If you don't have that base to begin with, people who will contribute to your first earnings and hype up your product, it will be increasingly difficult to start your start-up.