If we were justifying our expense as analogous to building a database of emails, then it was a database that only allowed you to access a tiny, randomly selected, subset each time it was used.

FORBES: Facebook Pages Are a Bad Investment for Small Businesses

The entire crowd-sourced database is too big to store on an iPhone, so we download an appropriate subset (cache) onto each iPhone.

FORBES: We Don't Want To Know Where You Are, Apple Says