It's similar to the 'flip-flopping' problem (I'm sure there's a technical term for it) - actions based on feedback from a sensor changing the sensor reading, triggering a different reaction.

A common example I've seen used is: Automatic headlights on a car turning on in the dark. When the headlights turn on when you're in a garage or tunnel, they can create enough ambient light to trick the sensor into thinking it's light, and turning the headlights off. The solution here is to add a delay into the reaction.

I'm wondering what a solution is to a problem with mapping - is it add a delay to re-routing traffic? Or rerouting traffic randomly? Or spread traffic out over a number of routes? It's made harder by the fact that Google in this case won't be routing all traffic - just a subset.