I looked into this long and hard and even built a website and minimal implementation, as I'd had some experience running and contributing to bounties on Open Source projects, but the more I thought about it, the less like a solid business it seemed.
The biggest problem is that the amounts involved are small, and the number of projects involved is also small (this is a $400 project, and it was considered interesting enough to get front page on HN; this indicates a tiny market). At the time, SourceForge, and several other Open Source sites, were beginning to add bounty and "hire this developer" features, and I couldn't see how a third party could more effectively reach those users or those developers (because you need both sides to buy into your product in order for it to be useful). The amount a third party could charge for the intermediary service is bound to be low or developers would go elsewhere; a couple points, maybe. So, 2% of $400 is 8 bucks. It'll take 10,000 projects of that size per year to pay yourself a decent salary and cover expenses. There probably haven't been 10,000 Open Source bounties in the past decade, much less the past year.
One of the problems a product like this would solve would be the trust issue: Can the bounty contributors trust the developer to deliver quality code if paid at the start, and can the developer trust all of the bounty contributors to pay up in a timely fashion if the code is delivered first. But, there are already ways to solve that problem. ChipIn solves the latter one, and many Open Source developers are sufficiently well-known in their community that no one would doubt they would finish the job. The other problem is connecting developers with money; but SourceForge and elance and many other sites already provides mechanisms for users to give developers money, as do traditional contractor agreements.
Of course, you've specified "digital content", and I was just looking at software, which opens up the market quite a bit. There were discussions amongst the browncoats (Firefly fans) of building a system to directly fund new Firefly episodes through viewer contributions. But, I think in the end, everyone agreed that the math just didn't add up. It might for lower budget content.
Back to software, I think github and SourceForge could make a few extra bucks from this kind of idea, but I don't think there's much room for any third party to fit into that relationship, if they aren't already in the loop for some reason.
The biggest problem is that the amounts involved are small, and the number of projects involved is also small (this is a $400 project, and it was considered interesting enough to get front page on HN; this indicates a tiny market). At the time, SourceForge, and several other Open Source sites, were beginning to add bounty and "hire this developer" features, and I couldn't see how a third party could more effectively reach those users or those developers (because you need both sides to buy into your product in order for it to be useful). The amount a third party could charge for the intermediary service is bound to be low or developers would go elsewhere; a couple points, maybe. So, 2% of $400 is 8 bucks. It'll take 10,000 projects of that size per year to pay yourself a decent salary and cover expenses. There probably haven't been 10,000 Open Source bounties in the past decade, much less the past year.
One of the problems a product like this would solve would be the trust issue: Can the bounty contributors trust the developer to deliver quality code if paid at the start, and can the developer trust all of the bounty contributors to pay up in a timely fashion if the code is delivered first. But, there are already ways to solve that problem. ChipIn solves the latter one, and many Open Source developers are sufficiently well-known in their community that no one would doubt they would finish the job. The other problem is connecting developers with money; but SourceForge and elance and many other sites already provides mechanisms for users to give developers money, as do traditional contractor agreements.
Of course, you've specified "digital content", and I was just looking at software, which opens up the market quite a bit. There were discussions amongst the browncoats (Firefly fans) of building a system to directly fund new Firefly episodes through viewer contributions. But, I think in the end, everyone agreed that the math just didn't add up. It might for lower budget content.
Back to software, I think github and SourceForge could make a few extra bucks from this kind of idea, but I don't think there's much room for any third party to fit into that relationship, if they aren't already in the loop for some reason.