[nckpark]

This doesn't prove anything about the quality of a 'startup idea' It just proves that you are able to convince a small number of people to drop five bucks. I don't see how that has a correlation to the future success of a business.

This would be much more interesting if it were pitched as a way to build a group of active early adopters. Pledging to an idea should give the user some perks from the start, and you should make it easy for the companies collecting pledges to incentivize these users.

[PedroCandeias]

You're completely right, and also just described Kickstarter.com :)

Although... kickstarter does seem a bit more oriented to creative and industrial endeavors than, say web app startups.

[Ntagg]

It'd also be cool to give the start-ups ideas of what kind of perks they could offer early adopters. I thought lunch with a founder was a fun idea, but I had trouble thinking of perks that were genuinely worthwhile and incentivizing.