I'm surprised that lots of people are surprised.......
I did a business degree at QUT and one of the units had a strong focus on Facebook and similar sites. There was no secret at all that FB sold information. The little scrap of advertising on their pages is a portion only of their revenue.
An interesting data gathering method not mentioned by the media currently was users photographs. Apparently FB has (or had) paid employees that were assigned users photos and literally counted individual items, for example a party photo would reveal XXXX , XXXX, Fosters , white wine , XXXX , Bundy Rum , Doritos, Cheesells , Winfield Blues, ....... it just went on and on. This is where they get data from people who are not even on FB. As your cameras and phones deliver higher and higher quality photos (with background data such as EOS6D GPS co-ordinates for each photo) and photo recognition software getting more advanced you will continue to provide saleable data.
The reason they did this was for reliable data. Surveying can get data but people tend to say what they would like but not what they actually spend their money on. Just simple observation reveals the cold hard truth.
FB did not build their web site costing million upon millions out of the goodness of their hearts just so we could share videos of cats falling in a swimming pool.
Facebook is far from alone , Myspace, Photo sharing sites including Flickr, Google and other search engines, Ebay, Forums, you name it they sell data.
The one that surprised me was at least one unidentified, (by QUT), car servicing company sells data to our federal government and fuel companies on how cars are being driven. Next time you are wondering why petrol is so dear and half the cars race off from the traffic lights next to you, black smoke belching from their exhausts, remember they just sent oil companies and the govt a message that although we complain and whine fuel is so expensive in reality most people are not trying to save it.
I do have a solution for this dilemma ..... take as many train photos as you can and put them the net. Its all we can do to break the data gatherers non train loving minds !