Amazon EC2 MySQL Databse server scalability

Hello,

We are looking for a solution to accomplish rapid (and, if possible, automatic) scalability for a remotely hosted custom forum software solution. Users will come to us and register their forums, which we will host for a fee, as well as lighter free version. We need to be able to scale to allow for large growth potential as forums grow on their own while we continue to recruit new forum startups.

I was instructed to look at Amazons EC2 services as they have scalability options through an API, making them apparently automatic.

My question is how can we setup with Amazon EC2 (assuming this is our best solution) to allow for an ever growing database requirement to be split among various servers and (as seamlessly as possible) scale to fit future growth either automatically or manually.

One proposed solution was to custom code the application around Amazon EC2 to communicate with its API to know when a server is/isn't needed and move forums from one to another as loads change. My concern with this is moving forums too frequently and having issues with write locks, database integrity, and overall chaos of rapidly changing database structures.

What is our best solution to launch this new service fairly small and have the ability to scale our databases?