I think it would be valuable for a number of reasons to have a community of researchers and research-funders rather than a general community of people that need money and people that want to give money away. The main reason being that it would make it more likely for experts to frequent the site and spend money (i.e. researchers could subscribe to a field of interest to get updates on new projects).

Also, I think the incentives would have to be different than current crowdfunding sites -- in some cases I think it would need to be donation based (which e.g. Kickstarter doesn't support).