If you forbid the app access to the camera via the Windows settings a System.Exception is thrown when you start the RadWebCam control. The exception message is 'MFCreateDeviceSource failed: E_ACCESSDENIED'
When run over Remote Desktop the webcam does not render anything. This is because D3DImage does not render when WPF switches to software render mode which happens when running an app over Remote Desktop. There is a possible fix for it implemented in .NET 4.5 which allows D3DImage to also fall back to software rendering.