Earlier quoted context omitted.
This has been possible before. Google was built around content based advertising. Also, maybe click-through rates are not that important? Maybe exposure is a more decisive metric? As a side-effect, we may reduce social bubble effects and maybe even return to a shared reality? (Many of the unwanted effects of the Web are really due to targeted advertising and its consequences.)
You're clearly under the impression that all that Facebook does is get you good click-through rates and low conversion rates. Similarly, you're under the impression that Google's conversion rates are through the roof. Did you ever stop to ask yourself if your world view might be limited to a small sample size (eg: your own experiences)? I know plenty of businesses where the conversion rates are exactly the opposite o…
P.S.: The general idea of targeted advertising misses the concepts of state of mind and focus of interest entirely. There's a (significant) difference in delivering a message in context and out of context. (The latter may have even adversarial effects.)