Norvig's Law: Any technology that surpasses 50% penetration will never double again

The universe is not static. And demands and supplies are particularly dynamic. Intuitively I see no reason why penetration percentage can't wax and wane with time due to changes in supplies, demands, populations, behaviors etc.

He obviously understands the implications of shifts in demand given his "what you count" argument. Why bother stating a "law" if you can see its own holes?

http://flickr.com/photos/7736808@N03/863738963/

That was pretty obvious. I guess it means you can't ride on the coattails of network effects after that point.

Of course you can. Once the Internet reaches 51% penetration, you don't think we'll be able to benefit from the network effects of connecting part (all just isn't going to happen...) of the last 49% of the planet.