Mr. Sterling states that 4 million businesses (2 million in the U.S.) have claimed their listing in Google Maps. And I quote:
let’s imagine what it would look like for Google if all two million US local businesses that had claimed listings were to advertise at the highly affordable $25 per month (or $300 per year). It would represent new revenue of $600 million.
That could pay for a lot of anti-spam technology.