But people advertise with Google precisely because they know the ads will be targeted at relevent people. If Google just sell loads of ad slots that just show to random users then that’s just a waste of money. If I’m selling motorbike helmets I don’t want to waste my money having Google show those ads to 60 year old men who only travel by bus or golfers or people who use wheelchairs.

Google won’t just sell loads of ads here, they’ll totally change their business model to something closer to the targetting approach.