But when you're robbed you'll know exactly who did it. I expect Google will try very hard to appear to treat all ads equally, hence the focus on all ads on part

But when you're robbed you'll know exactly who did it. I expect Google will try very hard to appear to treat all ads equally, hence the focus on all ads on particular sites, instead of trying to make judgements on individual ads. If they don't, they will quickly suffer massive fines that actually hurt their bottom line every year, as well as lawsuits from competitors that they stand a chance of actually losing.