Do you have a reference for this? I'm under the impression they only charge the cards once the funding goal is reached. Amex in particular only allows pre-authorizations to last up to a week.
1. If the project has met or exceeded its funding goal, all backers’ credit cards are instantly charged and funds go directly to the project creator.
2. If the project has not met its funding goal, all pledges are immediately canceled. And that’s it.
Amazon Payments is the only processor that currently supports these requirements, and currently Amazon Payments does not support non-US recipients — meaning that you need a US bank account and address to launch a project on Kickstarter. >>