I think small developers are their target customer, as well as big customers. After all, why would the big customer's care about the free tier? Similarly, why open the 'aws pop-up lofts'? https://aws.amazon.com/start-ups/loft/ If you are a big company thinking of using AWS, you probably pay a thousand bucks to send some of your engineers on a course to learn how to use it, or hire a consultant with those skills, you don't shlep down to the pop-up loft for their free 'ask-an-architect' sessions, free coffee and free candy.

It's self-funded startups and folks doing personal projects that those initiatives are aimed at, IMO, and they are the ones who would benefit from this kind of thing. By comparison, Google cloud (or at least appengine) does have billing limits, the daily ones reset each 24 hours, if you hit your billing limit, your instances just don't run until the limits reset.

To be fair though, the AWS customer service are always very quick to allow refunds, for small or large amounts. When I first started, I thought I had switched everything off, but something was still running and I got a couple of bills of around $20 over two months. When I complained, they refunded it, and were very nice about it. The are lots of cases online where they have refunded over $10,000 in fees to people who left their keys on github.

Maybe they figure the refunds are just the cost of doing business? However, I would prefer not to have to rely on the possibility of their post-hoc generosity when I do something equally stupid in future :)