I always say "rider on your ?????" that way the person has an idea of the size of the person passing them. and I had to put ??? coz lately it seems walkers have been walking on the left side of the path so I have to pass them on the right. If I'm riding with someone I always say riders of your ??? so they know there's more than 1 of us coming.

But I"m with ya CC - I had some guy blow past me the other day without saying a word, scared the bejesus outta me. Lately I've started chewing em out saying "next time say something please".