[belorn]

The issues with eroding privacy and with the amount of data needed to create targeted advertising are well explored, thus to expand the discussion a bit, lets talk about the subjects outside the scope of privacy.

Advertising, be that targeted or not, are problematic. In return for redirecting how people spend money, they distract people and steals time.

A child growing up is in average spending 133 hours watching TV commercials[1]. Add that with commercials on the web, games, and other media and the time spent on commercial is maybe longer for a child then what they spend learning a subject like math in school. If you then include the time lost from the distracting effect while reading email, or accessing a news site, and the cost of advertising to the individual goes up. People who's main problem at work or school is the ability to focus should strongly consider using tools such as ad-block. It could be the difference between graduating or not.

In contrast, opt-in advertising like recommendation services do not have those issues, and are in my view the only form of targeted advertising that are morally on the OK side. They use primarily legal methods in their businesses model, and do not need to use exploits and legal trickery to work.

[1]: http://www.statisticbrain.com/television-watching-statistics...