Screenshots of microPledge ("helps software get made and developers get paid")
micropledge.com
micropledge.com
Here what I've done: I use a piece of open source software. I want the developers to implement a feature that will be very useful to me. I offer to pay a considerable amount of money. They agree. I send them half. They complete it. I send them the other half.
A system that would let me share the financial burden and handle the whole process would be very useful. I said before that I think you should expect to see much bigger pledges than you're thinking right now. As a business, pledging $10k for a feature that saves me having to buy an extra $50k in servers is a no-brainer.
If you're going to be actually holding the money you will need to be extremely credible and your reputation spotless. A picture of who you are, your office (if you have one), street address, phone number, and that kind of stuff goes a long way. I want to make sure the authorities can find you if you do anything evil.
1) The pay-half-now-half-later thing is solved by our staged releases. The developer can say "I'm 50% done, can I please have half my pledge money?" And he'll get half his money if the pledgers are okay with his progress (if they're not, he might only get a portion of his money till they are happy).
2) The share-the-burden thing -- especially if you're talking big pledges. You could have your $10,000 split across 5 people/companies (or more, of course).
The Credibility Thing is a good point, and something we're very conscious of. We're going to be very open about who we are and where we live. And (very soon) we're also going to look into getting our money flow audited annually by a company like Grant Thornton.
P.S. Just wondering if you have a contact email/website somewhere? Didn't see one on your profile page.
I'm just a developer/sysadmin guy who frequently has the task of spending money on behalf of the companies I work for, usually on contract. Occasionally the best available option is to sponsor development. In my case I've basically dealt with the open source developer as a private sub-contractor.
Which actually brings up an interesting point. For various reasons some companies won't want others to know they're sponsoring outside development. You should consider giving sponsors the option of having their pledge remain non-public. Maybe even anonymous to the developer, which is an interesting thought.
Good luck with the business, I can't wait to see it when it launches.
Anyway, your FaceApps Developer Expo sounds like a sweet microPledge use case. Users can withdraw their pledges if a project doesn't finish on time (e.g., you don't get enough money for the event and decide to call it off).