[jcl]

However, if everyone carried 10-15 extra car-lengths ahead of them, the total capacity of the road would be greatly diminished; you would just be moving the jam to the on-ramp.

The peak performance of the system is actually a mix of altruism and selfishness.

[masomenos]

That's a fallacy, addressed by the site -- in short, the benefit gained by minimizing jams more than offsets the increased space between vehicles.

[jcl]

I think you may have misunderstood my point, which is that peak performance is attained when a few drivers drive altruistically (as the author does) and the rest drive "normally". If all drivers choose the same behavior (all altruistic or all normal), then the system doesn't work as well. This is interesting from a game-theoretic standpoint.

The author says much the same thing on his FAQ page:

If EVERY driver was to constantly maintain a HUGE space regardless of speed, then it would probably cause problems. The merge-zones might stop jamming, but the capacity of major highways would be reduced. On-ramps would become choked as traffic backed up into them, and there would be slowdowns extending far out into the countryside.

It is, of course, a purely theoretical problem, since there is no shortage of non-altruistic drivers.