Even if only 1% of people used adblock, then that's 1% of millions of dollars of ad revenue. It's easily enough to put several people on this as a full time job if they want to.

I'm sure Google saw it as only a minor issue at first, but the number of people using adblockers is presumably going up all the time.

The irony being of course that adblock usage is skyrocketing only because companies like Google have made the Internet so thoroughly ad-polluted it's intolerable to go without one.