Is it pure risk for the backers? e.g. if they make a product, they get something they bought, but if the product flops, they loose their money.
And now if the product makes a fortune, they only get their product they bought.
In other words, is kickstarter just a pre-order sales website?
It's zero risk for the kickstarter backers. There is zero chance they will lose more than they pledged through kickstarter.
Product? They didn't buy any product. Kickstarter has been quite clear, it is not a pre-order service. Anything offered in return for a kickstarter pledge is essentially a thank-you gift. Like all gifts, you're shouldn't demand one or complain when you don't get one.
If a kickstarter campaign fails (that is, raises the requested funds, but never manages to complete the product), the backers get nothing and have no recourse. I don't see how it would be any different if the campaign succeeds, as it did in this case. (Other than for P.R. reasons)
So back to the question of risk, once the campaign reached its funding goal, that money pledged was gone. Not a risk, but a certainty. It's like asking, what is the risk if I drop $5 into a Salvation Army bucket? No risk--you're just out $5.