Also, it has never been cheaper to make a movie, distribute it and fund it. On a kickstarter budget you could certainly make a film, as people have done in the past. Then, you can see if people want to watch the movie before you make it. Many people don't want to watch low budget indie documentaries, however the ones's that do are often willing to pay.
It depends what sort of film you want to make. For documentaries, that model can work quite well. If you want to make a narrative feature it's a great deal trickier. That's why the most successful Kickstarter projects in this area have been tied to existing franchises, eg the Veronica Mars film.
But suppose you have an original concept that's not a film version of a graphic novel and doesn't have a built-in fanbase: that's an awful lot harder to get interest for, and the methods you can use to get interest (eg sharing the script or key art or storyboards) can also limit your upside, ie the more you reveal to potential backers the less suspense you can create in the work itself.
It's doable and crowdfunding is definitely going to become an increasingly important business model, but it's still very far from an ideal approach. When I look at narrative projects on Kickstarter I can tell a lot just from the tagline, picture, and budget they're seeking. And for 90% of people trying to do a feature the prognosis is negative - either the quality is going to be dreadful, or the producers clearly don't know what they're doing, or everyone in front of and behind the camera is going to be working for free (with a correspondingly higher risk of non-completion). Unfortunately, the most competent ones (in terms of demonstrable ability to deliver a marketable film) are less likely to get funded, because of the amount of money they need to raise.
