Usually I use the Tor Browser to read news sites.
The last few times I have visited Hacker News, I have been intercepted by a captcha. That's OK. However, when the captcha thing use jacascript, and takes 4 - 5 iterations to complete - I'm starting to wonder if it tries to identify me as an individual - and not just as human. Especially when Google seems to be doing the screening (reCAPTCHA). I'm using the Tor network explicitly to prevent Google & Co from tracking me.
I guess all people will type on the keyboard or move the mouse a bit differently from others - and given a large enough window for the user interaction, it should be possible to create a unique profile. I have noticed that CloudFlare does the same thing - requiring several iterations when I point the browser at theregister.co.uk.
If unique identification is what's going on, I'm not OK with it.