Most silverlight apps use services to get data. I would add that abstracting out the service layer calls so that the silverlight pages load in the designer (either Visual Studio or Expression Blend) without the presence of the service helps out. Especially if the UI is being designed in Expression Blend. The some dummy data can be retruned without calling the service and the UI designers still get a feel for the look and feel of the application with data.

Most silverlight apps use services to get data. I would add that abstracting out the service layer calls so that the silverlight pages load in the designer (either Visual Studio or Expression Blend) without the presence of the service helps out. Especially if the UI is being designed in Expression Blend. Some dummy data can be returned without calling the service and the UI designers still get a feel for the look and feel of the application with data.