The one thing that has stopped me using AWS or Azure is that I can't top-up my account and know that it would use more than the available funds. It might not make business sense but I will never sign up for something so open ended as AWS.
This problem turned up in recent HN discussion. [0]
Turns out it's possible to get billing alarms from AWS, but it's not something they make terribly easy. I don't know if it's possible to configure a kill-switch the same way.
My favourite AWS billing horror-story involves Glacier. Its pricing model used to be the stuff of nightmares, and caught plenty of people by surprise. [1]
