This is another level up (down?) from the standard "gotcha, b####!" post-usage metered cloud service billing that requires a credit card up front which is the main business model for a surprising number of internet companies. They can keep doing it because a significant percentage of their business is from startups that are burning through someone else's money.
But it's interesting that the only real difference is that they let you proceed without putting your credit card info in.
But it's interesting that the only real difference is that they let you proceed without putting your credit card info in.