Originally Posted by SSP
On the semi-rural roads where I ride, I use mine to ride more assertively. If I see a car coming up from behind me, and the car is not moving over to the left to give me room, I'll intentionally start to drift my bike subtly to the left (when the car is still well behind me). In nearly all cases, this will cause the overtaking driver to start moving a bit to the left also. As they get close, I drift back to the right, ensuring maximum separation between us as the swing around.
Even if it's some *sshole trying to give me a close shave, by forcing them just a bit to the left, I then have some space to my right to dive into as they get close. Using the mirror, I can monitor them as they get close and come around...I'm hardly ever surprised by a car's passing.
This technique would probably not work in an urban cycling scenario, but where I live it seems to work just fine.
An excellent point to bring up. I do the same thing. In most places it works great. In a narrow lane where one has to take the lane you can see when the cars behind slow or move over. You can also see the cars behind if you need to move to the left lane, of if you need to go across the whole road for some reason.
The best part is you don't have to turn your head (when you get good at it) and you can still see what's in front of you at all times. It's just plain easier.