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
But do you really need SQL Server? Can't you live with PostgreSQL or MySQL? Both have proven to be ok for most tasks.
Now if you need SQL Server features then you're out of luck.
Another option is to rent a server. How expensive is expensive?
(I've used Amazon S3 to store images for an application, it's ok and works fine, at least for that)