We Hate Requiring a Credit Card for the Free Trial, Too
It's kind of lame to require a credit card for a 30 day free trial, we agree. But our billing system, Chargify, works much better that way, which is the main reason. As regular internet users, we hate this as much as you. SORRY.
If you don't want that, you can also log in and go to Account >> Plan & Usage, and then change the plan to free.
Also, as a small company of six people trying to provide research tools to mostly businesses, people sometimes place our JavaScript on their site and then either don't want to remove it or forget it's there. That is totally cool with us, but in aggregate it vastly increases our server load, and requiring a credit card at least gives us some recourse if folks leave our code active but don't want to pay.