As has been stated by a few here already, this is just silly. If you fund one of these projects, you are simply a beloved donor, and that's as far as your relationship goes. You get rewarded with token gestures like T-shirts, or having your name up in lights somewhere, but that's it. It might be nice if there were a way to invest in these companies, but I suspect that would be legally and financially complex to say the least, even if it were made legal.
I wonder if people who donate money towards towards making a movie expect to get a cut of any backend royalties?