According to this, the Access types better cover their A$$es:
"The default database for WebMatrix sites will be the new SQL Server Compact Edition (CE) 4.0, and the really great thing about this is that you do not need to negotiate with your web host to deploy it so long as they have .NET 4.0 installed. When you build your site within WebMatrix, the database engine is deployed within the bin directory, with the sdf data file residing in the App_Data folder. The new version has been evolved to support medium trust and can be deployed easily in a shared hosting environment. CE has a number of limitations compared to its grown up cousins, but those limitations are not likely to prevent WebMatrix causing the death of Access as the most popular viable free, easy to install web database. WebMatrix also includes tools so that upgrading CE to SQL Server Express or higher is pretty much a button click. The file size limit is 4GB at the moment, but Microsoft are looking to increase that."
(from: http://www.mikesdotnetting.com/Article/145/Introducing-WebMatrix-An-Easier-Way-To-Do-ASP.NET)

Amazing VFP already does all this stuff (except is 2GB limit of course) and is easier! My advice is to watch how this stuff plays out in web development (which includes phones clients, tablets, etc). IMO, M$ is playing catch-up now...