I thought I remmebered this, and just confirmed it. Go to http://aws.amazon.com/free/ in an incognito window. Click on 'get started for free'. Pretend you don't have an Amazon account and create a new one -- you have to create a new account with a credit card, before finishing up and going on to 'get started for free.'

However, with Amazon, I'm pretty sure that they won't charge you if you don't cancel in X days. They'll only charge you if you later opt in to a non-free service. (But am I wrong there?)

Nobody thinks it's shady, but then, it's a large company everyone's heard of.

I assumed the reason in part was to lower any barriers to later signing up for a paid component of the API, wit one click.

I understand why OP is doing it, but I still totally think it's shady to have you sign up for a free trial, and then start charging you at a certain calendar date unless you explicitly and manually opt out. At least, if you're doing this, you better be very very clear that's what you're doing when you get the initial sign up -- but the clearer you are, the more harm you're probably going to do to your conversions.

This is why most services these days, seem try to give a trial limited on resources of some kind rather than calendar. You get up to 4 Widgets on the free plan, you have to upgrade to the paid plan for 5. Get ads on the free plan, upgrade to paid to not have em. Get 4k page views a month on the free plan, etc. You get public repos on the free plan, need to upgrade to paid for private. Etc.

Note that the services that offer that kind of free trial seem especially beloved.

Can you think of popular and beloved cloud services that offer a time-limited free trial after which they will automatically start charging you unless you explicitly opt out? I can't think of any.

Even the new york times, when they give you an initial X month subscription at 25 cents a day or whatever, and then when it's time to renew it's gone up like 500% -- you still have to actually opt in and choose to renew your subscription at full price, they don't just charge your credit card.

If you're not ready to pay, then why the hell are you trying my service?

It's not a charity, it's a small amount of money each month.