I teach Ruby on Rails video courses online, and I use c9 as the cloud development environment in all my courses. It's great because it's free, it's online, everyone has access, and everyone's screen looks the same (great for teaching purposes). Plus C9 works really well...
I don't think they used to, but now it appears that C9 requires a credit card to sign up for their free accounts. I'm guessing this is the first bone headed move Amazon is making since acquiring c9 a couple months ago?
My students are pissed. They don't want to give a credit card...some don't have one (they can buy my courses with paypal).
Come on C9! Don't be that guy!