[bryanrasmussen]

unfortunately you only have the willingness to pay before the product or feature is delivered.

[onion2k]

That's not true at all. You can charge customers before you build anything - it's just the 'pre-order model'. Lots of businesses do that, including some high-profile startups. Check out the sites like Seedrs and Kickstarter for examples.

[bryanrasmussen]

that's true, I guess in that case you do know that people really, really want it. Seems most suited to something obsessive, like games.

I tend to discount it as I have never paid for something on spec.