DesignData MVVM support in Blend, VS2010 and WPF/Silverlight

When developing a solution using WPF or Silverlight, there are normally designers working in Blend and developers working with them in Visual Studio 2010. Often it is impractical for designers to use data from live systems (e.g. they don’t want to install SQL etc.) but they need data to flesh out the user interface so that they can style it and edit templates. For example a ListBox with no data