One of the major arguments against the usage of Rich Internet Applications is the difficulty to measure usage and user interactivity compared with traditional static or dynamic web sites.

It seems that Silverlight is making that quite easier and here you can find a white paper discussing how you can apply web analytics in a Silverlight based application. Source code is also available.

http://xmldocs.net/Analytics/Using%20Web%20Analytics%20with%20Microsoft%20Silverlight.pdf