Actually, about a quarter of the things I want at the supermarket are missing about half the time.
Keen is much closer to correct than most of his detractors.
Markets are not about equilibrium, they are about disequilibrium. Look at the suite of exponential drivers that Ray Kurzweil identifies. They are not compatible with equilibrium models.
One of the major drivers of profit is disequilibrium.
Keen is far closer to reality than mainstream, and even his functions fail to capture the real complexity present.
If you can imagine a distribution curve, you will find an example of it somewhere in the preferences (genetic, cultural and intellectual) of some group for something. Very few of them are anything like straight lines.
Expectations vs time form complex topologies across populations, and the work David Snowden has done with his sensemaker suite is a much closer approximation to reality than any set of economic models.