Cool hack! How did you implement this? Care to share the details? You mention Route 53, but I'm curious to learn more. What does the stack look like? How do your update zonefiles, assign subdomains etc.?

It would be fun to hack on this + a cryptocurrency component - let's say, zzzzcoin - people can pay an incredibly small sum of zzzzcoin per request. This could be used to deter spam, remain free/affordable, reward early adopters, and turn into meaningful revenue.