Is it that hard to say?
After reading Vanilla's recent post on cyclists, I decided I'd pile on the anti-cyclist rhetoric. It's not like I haven't done it before.
My main issue with cyclists is when they don't warn you that they are approaching from behind. Granted, cyclists are not the only guilty culprits of this anti-notification trend. I've had runners spook me on the path when they suddenly appeared in my peripheral to pass -- not very often, mind you, but it's happened. However, it seems cyclists are a large percentage of the pass-but-don't-tell population. I'm guessing it's because they don't get passed as often and don't realize just how quiet they are.
Even if you're not a lead-footed runner like me, it's hard to hear anything coming from behind you. And that's true whether you are walking, running, biking or hula-hooping.
Have you ever noticed how the human ear is oriented to hear things in front of and to the side of the body and not so much to the rear? The pinna, for most people, is angled away from our backs. Furthermore, if an object is approaching at a high rate of speed, the Doppler Effect reduces our ability to hear it and react in a timely manner.
Physically and physics-ally, we runners can't hear you ass-hat cyclists (or you jerkface faster runners) zipping up on our backs. We'd get out of your way if we could hear you. Just remember that when you have to swerve off the path and end up flying over your handlebars because I didn't move when you didn't say "on your left." Stop being such a douche bucket and let me know when you're passing. And do it before I can see you out of the corner of my eye.