Google App Engine is a service provided by Google, free of charge for small to medium-sized projects. Google App Engine is a framework for Python or Java for writing web applications; the remarkable thing about it is that applications written in Google App Engine (GAE) can be uploaded to and run on Google's servers, using their (almost) infinitely scalable database engine. Theoretically, you can publish an application there which grows from 1000 to 1.000.000 users within a week without ever having performance problems or similar, making it a promising platform for online games.
Sounds great? Yeah, it does.
So, what's the problem?