I find that most people (except for cyclists of course) don't respond to 'on your left' because it means nothing to them. So on bike paths if i'm passing joggers, etc, I say EXCUSE ME. Everyone knows what excuse me means. O course, if they're plugged in to their stupid walkman, tough **** if they can't hear me. Sometimes I just snap my fingers in their face- so rude! But too bad.
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You can catch more flies with honey than with vinegar. That's great...if you want to attract vermin.