"Tracking users" has lots of uses. For example, we were trying to do OP on gwern.net for a while, using several of those tricks. It failed miserably and we coul

"Tracking users" has lots of uses. For example, we were trying to do OP on gwern.net for a while, using several of those tricks. It failed miserably and we could never figure out why. What evil things were we doing? Well, I wanted to know if people were using the links I put inside popups, like to Google Scholar. Was anyone using them? If not, they were just so much clutter and should be removed for the users' benefit. I also wanted to get a list of outbound links by popularity, so I could write summaries/annotations for the most popular unannotated links, and rank dead links by priority for fixing (there are too many unannotated or dead links to 'just fix', so a ranking would've helped a lot). But the link tracking never worked, so, I couldn't do any of that.