I inspected the source code of Google's reCaptcha offering and was disgusted at how many bits of information they were collecting. They also seem to be fingerprinting users so they can't keep registering new accounts on a platform, locking out anonymous users who are usually the best types of users on the platform, as IMHO anonymous voices are (usually) the best voices, or at least the more interesting of voices.
Google's reCaptcha code seemed to be very keen on knowing my 'cadence' or the way I used my mouse and how quickly (or how slow) I completed the captcha. It also looked at things like timezone, screen resolution, battery charge level etc So they could determine if it was 'you' who was using the captcha, soon after, in a separate session (even on a different device!)