There's kind of a long-term issue about the web platform changing in ways that increase trackability, often without people thinking about it (or maybe in a few cases without people admitting that they thought about it).

There is a W3C TAG document that touches on this at

http://www.w3.org/2001/tag/doc/unsanctioned-tracking/

One problem is that there are so many ways of tracking user-agents in the web platform today that it can be hard to convince anyone that addressing one of them will improve the situation. :-(