Probably put together by idealists who haven't left the renaissance, where artists had patrons who were wealthy beyond belief, and supported the lives and efforts artists in return for painting portraits of themselves. "Hey, Gus! Michelangelo wants another hunk of marble- can you send your surf down to Cassius and pick one up?"
Even in those times though, artists had to sacrifice integrity to a financier, and I don't think posting a note on the "town pole" would've convinced the blacksmiths and bakers to throw in their half-pennies for a collaboration.
In this capitalist, narcissistic, and hollow world, we artists have a new patron- it's called the government, and welfare. And those don't even come with any guarantees... and contain their own levels of censorship.
So imagine, if you will, the difference between one "benefactor" with twenty grand, and 20,000 benefactors with a dollar each. That's a lot of pockets that will want a refill (the shipping costs alone would negate the benefit of spreading the cost), and "investors" with different standards and expectations for the final project (even if you DO finish your project, if some religious person doesn't like the main character being a smoker, you might have to refund him, or at the VERY least, DEAL with him). Now, granted, this looks like a "pay, forget, get paid" kind of deal, but if that IS so, then why would someone throw the money there, and not at the stock market?
Imagine you're a rich film financier. Are you gonna find this site and say "hey! I happen to have extra cash- let's throw it around!".. No way! And I don't see a poor artist like myself checking it daily for fun new projects to anonymously throw cash at. Come to think of it, I don't see ANYONE doing that.
So I'm putting my chips in with Oaksterz.