A good classifier will take into account interactions as well, so if 80% of the people who like both Top Gear and Glee are heterosexual, then they can still get some predictive power. Further, if 90% of people from your city are heterosexual, they could take that into account as well. And that doesn't consider the internal stuff that Facebook knows (and can sell to advertisers), such as the demographic profile of the people near your IP address.

It's not just averages of society, it is individual profiling. At it's most benign, it will target ads that it thinks your demographic profile will be most responsive too, but at it's worst, it could certainly be (mis-)used for individual persecution.

This. But it is an argument between someone with the car data recorder versus someone who buys ink by the barrel, so get your popcorn, pull up a seat, and enjoy the show!

He has numbers, but where did they come from? Does anybody looking at the story from this distance have any way to verify that the data in the blog post is unadulterated, accurate data from the trip in question? Just because someone uses a bunch of numbers in their argument they shouldn't automatically win the day. Look, I highly doubt he's making up the data but the question of whether he is shouldn't be dismissed out of hand.

A quote from Matt Yglesias: "Amazon, as best I can tell, is a charitable organization being run by elements of the investment community for the benefit of consumers."