you've never met a federal grants administrator, have you? I've met only two non-stupid ones, ever. The first was my neighbor as a child (who was a physics administrator for the NSF who had the foresight to argue to pull the SSC - because of serious problems with the site - to say the least), the second was my former boss, who quit her highly successful position in academia (long story, won't get into her reasons for doing so).
To be less flippant: There's MORE accountability. If you crowd-fund, people will criticize you publically. when was the last time you saw public comment on an NIH grants review? On a DARPA Call for Proposal? If you don't take public money, to a first approximation you get ONE chance to screw things up by dazzling people. The next time, people are more likely to be wise onto your shenanigans.
Think of it this way: Yes, there are spectacular failures on kickstarter. But yet, there are still good projects that get funded. The economic model, despite all of its naysayers, STILL works to produce good content. Think of all the video games that have successfully migrated to the platform with private micropatronage, and contrast with this: http://www.slate.com/articles/business/moneybox/2012/06/_38_...
Now, consider that this may be happening in publically funded academic science (Arsenic Life, for example).
I agree that a kickstarter for science would be an interesting experiment. It would be quite a change for scientists, if they have to propose to the public instead of experts and politicians.
I'm in Germany, so no direct experience with the US system. Nevertheless, the symptoms are the basically the same here.
Well, I'm biased, since that's what I'm doing (details in my profile). I have strong opinions about how it should be done to be honest with your donors.