what portion of all the other driver's around me also looking at google maps? Is Google Maps telling them to take the same alternate route as me? Are they all going to do it? If they all do it, does the alternate route (which likely can't handle as much traffic as the original route) just became as jammed as waiting in traffic? Or even worse, if they're all going to do what google maps says, would I in fact be much better off ignoring it and sticking to the original route?
It's hard to tell what's imagination/selection bias, but following google maps traffic-jam-avoidance suggestions has seemed disastrous enough to me enough times that I mostly just stick to the original route now. (Of course, one could also imagine using one's own route knowledge to pick an alternate route of one's own without google maps...)
I suppose google maps could be smart enough to tell half the people to go one way and half the other... I kind of doubt it is, but one could imagine a computerized route direction system which, if enough driver's had it, could actually maximize efficiency by sending different drivers different routes intentionally... I'm not holding my breath for it.