I ran across this good post today while searching on using objects represented as a MonoState or Singleton pattern in WPF databinding:

Monostate vs. Singleton : Adventures in WPF Databinding [The .NET Addict's Blog]

The gist of it is that objects represented as a MonoState may not work property with property update notifications.  This kind of makes sense as the UI will be bound not to the actual object, but the wrapper around the internal singleton.  Hence, property change notifications on the singleton may not make it up to the UI since they bubble up but there really isn't anywhere to go as they are not actually bound to a UI control.

So, the summary is be careful if you do this.