Joel, I like that usage - it removes some of the guesswork, especially if several developers are involved. I actually thought that's what the parameter's intention was (going from the name too) but then saw other examples that worked in a different way.
Cliff - I understand what you are saying. At the moment it's a little hard for me to see the benefit as it just seems to increase the knowledge you need to have about each notification. I guess it's a matter of providing thorough documentation.
cheers - Nils.