If you are talking about kickstarter and the like, no, there is a very real chance you will not be able to buy it if you don't fund it. There is also a very real chance that you won't get it even if you do fund it. And if it doesn't get funded in the first place, there is zero chance. Unless you were referring to some other sort of funding process.

FWIW I do not participate in kickstarter, but that is because I like having things I spend money on. I know plenty of people who do. So, I think it's in general a good service.