If it fully funds, then no. They set their goals. If say they ask for $250,000 and only get 50k in support they you don't get charged.
But if they ask for 50k and it gets 250k or fully funded, you're charged whether or not you ever get the project or not.
According to kickstarter themselves 6-8% of projects never get fulfilled. It's up to who's proposing the project whether or not they will do any good faith returns or credit but kickstarter themselves are hands off. And outside of Peak Design and a few other established companies most who use kickstarter are using it for the sake that they don't have the resources to develop the product themselves and don't have the funds to back a failure .
Interesting. Good to know.