I met the guys from KillBill at the Money 20/20 Hackathon and I think they're doing a great job with their platform, which is already serving big players like GroupOn. They clearly know the payment ecosystem and this is a good way to set up billing in a way that does not lock you in and gives you flexibility for the future as you scale your business, including Fraud Prevention plugins. Disclaimer: I'm product lead at Feedzai, one of their supported Fraud Prevention solutions.