Do you follow Composite Application Guidance (formerly code-named "Prism") in your Silverlight (and WPF) Projects?

The Composite Application Guidance from the patterns & practices team at Microsoft is designed to help you more easily build loosely coupled, independently evolvable modular WPF and Silverlight client applications which take advantage of the capabilities of WPF and Silverlight.

With Composite Application Library (CAL), you can only adopt the components your application requires. For example, you could change your communication approach from .NET Framework events to use the Event Aggregator, which allows you to send loosely coupled messages between modules. Composite Application Guidance