Right now account sign up is wide open, but the plan is to move to paid accounts with a free trial period. I'm thinking tiered plans based on concurrency limits (right now all accounts are capped at 1 active instance).

The use case not highlighted by the blog post is is disposable databases for use with automated tests. One of my inspirations was the idea of using a Vagrant VM as a development environment and deleting each night and re-creating it each morning so that the project doesn't accumulate untracked dependencies on environment tweaks. I'd like to enable/encourage similar practices for DBs. For that, I'm working on a Jenkins plugin.