Money is the mother's milk of polictics, so the saying goes. That holds for advertising too, and the big thing in web advertising is targeting - presenting ads that are more likely to the interesting to the person on the other end of the web browser. More interest, more clicks; more clicks, more revenue.
On the other side, it's palpably creepy to have advertisers doggedly monitoring every single thing you do - and many of us wonder what else that data could be used for? It's not like data ever goes astray or is used beyond it's original purpose, is it....?
Now, there is another feather in the advertisers quill - using high-frequency sounds to sneakily talk between devices (like a TV and a tablet), to better track your habits across devices.
ArsTechnica"As a person goes about her business, her activity on each device generates different data streams about her preferences and behavior that are siloed in these devices and services that mediate them," CDT [Center for Democracy and Technology] officials wrote. "Cross-device tracking allows marketers to combine these streams by linking them to the same individual, enhancing the granularity of what they know about that person."