In the current status quo, there is a data détente that keeps either solution from happening: advertisers don't want to give third-party websites intimate knowl

In the current status quo, there is a data détente that keeps either solution from happening: advertisers don't want to give third-party websites intimate knowledge of ads vended because they don't want to compromise user privacy (or more cynically: they don't want to give third-party sites so much info about what ads are run to what users that those sites cut out the middle-man and just broker adds to run for users directly). But third-party sites don't want to give intimate details of users of their site to ad companies for symmetrical reasons (Google has dipped its toe into social media before). If the industry moves to a place where only server-injected ads are profitable, something will surely give here. The end result will be more large conglomerates knowing more about us than ever before, unfortunately.