>>Even a better example is how a Windows message queue processes messages. Ever use Spy++ from the VS tools to view messages that an app receives? It's amazing that the whole thing doesn't slow to a crawl.
>
>Boy, have you got that right! Whenever I work with that feature, I have to remember to mark what messages I'm interested in. Otherwise, I can't see what's going on.

Same with regmon.exe from www.sysinternals.com. Little did you know how hard the registry gets thrashed.