I actually ran a successful campaign on Indiegogo with flexible funding (gasp). I originally wanted to do Kickstarter because they seemed more credible, but Kickstarter doesn't allow you to promise any of your funds to charity. Half of my funds were going to charities, so Kickstarter wasn't an option.
So, off to Indiegogo I went. Flex funding is actually the default option. I changed it, but they informed me that without flex funding, you will NOT be able to accept credit cards. With flex funding, you get the money immediately. Well, paypal money at least. Credit card funds come a couple days after your campaign ends. A friend asked me if there was anything stopping me from taking the thousands I raised and running with it. Really, there's nothing stopping people. So... on Indiegogo you can promise to donate money to charity, get money immediately, and take the money and run. But, if the person was honest or not, Indiegogo still gets a cut, so I bet they don't care. They really really want you to do flexible funding.
One more delightful thing: my campaign was "trending" on the website. I was thrilled that it was on the popular section with Solar Roadways! However, on the list I was right next to a sex toy that claimed to give men the best blow jobs ever. Mine was about helping disabled cats in shelters, so my cute cat icon was right next to a fuck toy.
Mortifying. Thanks Indiegogo!