Kalamabana + Kevin,
Right on you got the idea and it usually works well does it not. I notice a lot of the better guides use the aproach that you are both talking about when aproaching a person wading a run that's somewhat narrow. Usually they hold in the current far enough up above the person wading and ask how they would like to be passed. I like it when they walk or drift behind me and it won't bother me a bit to stop casting for awhile and let them pass. Just makes sence because no one has to get uptight, you can even carry on a short conversation about how the fishing has been. That's a lot better than the usual one person stare down and the boat guy rowing by with his head down so he don't have to look ya in the eye.
To me that's one reason drift boats are better for a river than jet boats. The drift boater has the opportunity to work with the river and those who fish it. Not saying jet boaters are a-holes just they always want to go a million miles an hour up/down a river fish the same run 10 times and scream off to another place like it maybe the last 10 minutes that they ever get to fish.