this guy is an idiot. the whole point of other products, 20% time, diversification, etc. are to not only create other cash cows but allow tolerance for a product's growth/earnings to slow down. ever hear of "don't put all your eggs in one basket"?
the simple fact is, when you have a cash cow, you got extremely lucky. it's really hard to duplicate that so you do your best to support it and keep it going by creating an ecosystem around it and expanding it wherever you can. see: gmail, google webmaster tools, MS SQL server and friends, and so forth.
his real gripe seems to be, though he may not realize it, that companies aren't operated as short-running events that generate a burst of money for shareholders and then fizzle out and die. he doesn't seem to like the long-haul approach that has kept e.g. MS in business for 30 years.