I believe that "meme" in this context is being used within the dictionary definition of the word, meaning "an idea, behavior, style, or usage that spreads from person to person within a culture" according to Merriam-Webster.
That's the definition I'm using. I don't understand what's so noteworthy or funny about that example for it to become a meme.
I'm guessing, but presumably "pizza in San Francisco" is a representative GIS problem that pushes all the right buttons and acts as a good shakedown test, and has become a "standard".
I thought it meant that Google et al are all trying to solve the "pizza in San Francisco" problem (i.e. trying to find local businesses) and not trying to solve the problems that people are actually turning to maps for, because "pizza in San Francisco" is an obviously-monetizable problem.