In this walkthrough, Mihail Mateev shows how to create a LightSwitch application, using as data source WCF RIA Services.
Source: Mihail Mateev's Blog
LightSwitch is primarily targeted at developers who need to rapidly product business applications.
Visual Studio LightSwitch application could connect to a variety of data sources. For now it can connect to database servers, SharePoint Lists and WCF RIA Services .
Connection with WCF RIA Services requires some settings that are not "out of the box".