Don't get me wrong, it's pretty slick!
Of course abuse or market fluctuations could be costly, but there are built in limits. And thanks!
Also, I noticed a public key in ~/.ssh/authorized_keys. Is that intentional or just part of how EC2 APIs work?
Other than that, great job. I would definitely use this service.
Curious to hear what you and others use this for--I built it because it's cool, but still trying to put my finger on the biggest use case(s). So far people have told me they're having fun with 'rm -rf /', fork bombs, and getting a decent python shell in the browser ;).