Online Trackers Follow Our Digital Shadow By ‘Fingerprinting’ Browsers, Devices

http://www.npr.org/sections/alltechconsidered/2016/09/26/495502526/online-trackers-follow-our-digital-shadow-by-fingerprinting-browsers-devices
how fingerprinting can follow you across devices
This is best seen if you think about you as a traveler with two different devices, let’s say your laptop and your mobile phone. What some website or tracker is going to observe is that there are two different devices over and over again connecting from the same networks, from the same set of IP addresses. … Over time, that allows this online tracker to put together a profile of the behavior of those two devices and infer statistically, with a very high degree of confidence, that this pattern of coincidences could not have happened by chance — it must be because these two devices belong to the same individuals. …
 
For the most part, these are very new and interesting technologies, but also creepy from a privacy perspective and more-or-less unregulated.
On the uses of online tracking  The most obvious consequences are certainly going to be online ads that you see and targeted offers that you get. Occasionally, we know that websites have been experimenting with price discrimination based on your online activities and trying to infer if you’re a more affluent or less affluent type of consumer online. That’s not so widespread yet, but there are a few studies that have revealed that it does happen from time to time. …