Once you giveth the money, you cannot sayeth how they (legally) spend it...
If you give money to a specific campaign or project ou can specify how the funds are to used when you give it it becomes a more formal contract, than jsut giving away a few dollars. You can also request proof of how the funds were spend.
Otherwise funds go into a general operating fund.
Not sure where you get this from?
If you take their indiegogo campaign - if you pledge $15, you get a copy of the script in PDF form. If they don't make the film - what is you haven't received?
there are a couple of things like being an extra that you *might* be about to complain about if the film didn't get made but the vast majority of rewards have nothing to do with a film being made or released.
there is certainly nothing there that would give you the control you mention.
More than a couple... DVD of the film, download of the film, name on the credits in the film, etc.. Most importantly donating your money to a film that did not get complete because of over estimations of what fans would donate.
@Jedi Master
No one handed them a million bucks tough, they got 638K and used it all on a business then made an assumption fans would shell out 1.3 million for the film.
Concentrate on getting the base level from the fans so you can make the film, then you can run further campaigns to enhance the production. Don't collect 638k from fans and tell them you cant make the film unless you get 1.3 mill (or 600k to do half the film) more. Especially since it was not originally worded that way on the first Kickstarter.