"There is certainly ample evidence that "on your left" is mistaken for "move left" far too often. If your are a fast rider in mixed company you just need to cool it when necessary."

I *still* get startled and move to the left when I hear this. I personally hate when cyclists yell this. It's their responsibility to make sure they have enough room to pass safely. IMAGINE if cars honked at you just to let you know they're passing closely?!?!?!