It has started
Next the will be manipulating rankings. Only a little at first, then increasingly so until the search engine becomes useless. As a publicly traded company you have to have quarterly revenue increase. The only way to do that is to keep earning more money, and as an advertiser you can't do that without ever more ads. Eventually you get to a point where you have so many ads your service is useless, then the next IPO comes along and kills you, until the same fate befalls them.