Google Analytics recently added a "Demographics and Interests" feature to its set of tools measuring website traffic. They amass this data basically by what kinds of searches you do, your Google+ account, the sites you click on, etc. To see how accurate a picture it has drawn of you, click the following link (updated):
https://myadcenter.google.com/?hl=en&sasb=true
UX Quote of the Day*:
"The designers of the Phelps farm tractor in 1901 based their interface on a metaphor with the interface for the familiar horse: farmers used reins to control the tractor. The tractor was steered by pulling on the appropriate rein, both reins were loosened to go forward and pulled back to stop, and pulling back harder on the reins caused the tractor to back up."*
The authors go on to say:
"It’s clear in hindsight that this was a dead end, and automobiles have developed their own user interfaces without metaphors based on earlier technologies."
*Don Gentner and Jakob Nielsen. 1996. The Anti-Mac interface. Commun. ACM 39, 8 (August 1996), 70-82. http://doi.acm.org/10.1145/232014.232032
