It sort of puts paid to the idea of progress.
There's also a related "law": “What Andy giveth, Bill taketh away.”
I used to think this was true. For me, the perceived inflection point where perceived speed of software started improving was somewhere around 2008. This may be because I switched to a mac in 2006 and the releases around that era had a big performance focus.
I'd imagine that, until broadband becomes truly instant, you will have a need to ensure users that the page is still loading. A user's patience will never grow. It will only shrink. The least we can do is buy ourselves precious seconds by using a progress bar. It is the difference between "Your call is important to us, please hold" and "You are now 5th in line to be answered. Please hold." The illusion of progress goes a long way in fooling the user's brain into having just a smidge more patience.