The analogy is helpful, but leaves some things out. In one of the grocery stores, you'll find that if the lights flicker off and for just a second, half the products on the shelves may end up unusable. And if your store gets past a certain size, a sinkhole may appear and suck most of your inventory underground with no warning.

The only reason I can think of for using MyISAM tables in a web app is the terrible default InnoDB settings in MySQL. Users unfamiliar with InnoDB may not realize that the awful performance is an artifact of bad configuration, and easily fixed.