Try looking up Noma, Copenhagen the best restaurant in the world (presumably). It then shows locations of other restaurants in the area. Aren't those ads?

As what is reasonably expected (an this is old): https://www.forbes.com/sites/kashmirhill/2012/02/16/how-targ...

It is not a slippery slope argument, because they have that data and can use it as they see fit. I just suggested 2 ways in which Google can make more money with information people shared with them. Why is it reasonable to expect them not to do it?