It seems that Code4Lib hasn't discussed this., though the news is 2 weeks old. It seems that there are libraries using social share tools from AddThis", a company that has been using a technology called "Canvas Fingerprinting" to track users. 

In other words, it looks like libraries are giving away the user-privacy store.

For example, AddThis is used by my public library's Polaris catalog (BCCLS).

I'd be interested to learn how widespread this is.

Here's the article from ProPublica.
http://www.propublica.org/article/meet-the-online-tracking-device-that-is-virtually-impossible-to-block

And a follow-on discussion from Princeton CITP
https://freedom-to-tinker.com/blog/englehardt/the-hidden-perils-of-cookie-syncing/

The research article:
https://securehomes.esat.kuleuven.be/~gacar/persistent/the_web_never_forgets.pdf

Techdirt:
https://www.techdirt.com/articles/20140721/14523127960/tons-sites-including-whitehousegov-experiment-with-tracking-technology-that-is-difficult-to-block.shtml


Eric


Eric Hellman
President, Gluejar.Inc.
Founder, Unglue.it https://unglue.it/
http://go-to-hellman.blogspot.com/
twitter: @gluejar