I too tend to let drivers know my distain when the cut me off, especially the ones who do it intentionally!
On the other hand, I have started doing Positive re-enforcement when I see drivers that see me and give me the room I require. If they take that extra 10 seconds to let me pass before turning left in front of me, I give them a full hand wave and a nod of appreciation, as opposed to the single finger salute.
I believe that if enough people start doing this it may spread... but then again, I've been wrong before. In any case it doesn't cost anymore to try!
later, Tom.