Has anyone considered using something along the lines of the Amazon SimpleDB data store as their backend database?
SQL Server hosting (at least in the UK) is expensi
I haven't used SimpleDB, but have been using combination of S3, EC2, and MySQL for our application.
As long as you are willing to use SimpleDB, then you might as well consider using MySQL (which is very scalable, and not that expensive).
On the S3 and EC2 side, it is great in practice as well.