Let us analyze this further. Suppose that Alice browses 4chan. 4chan uses a Google image-classifying captcha. Alice is viewing user-generated content posted for free, including 4chan advertisements. When Alice chooses to post, she completes a captcha for Google and her post is sent to 4chan.

Who gets paid for 4chan's content? Alice does not profit. 4chan's users do not profit. 4chan 'profits' via advertising revenue but they actually operate at a loss.

Who is left to get paid? Google. Google gets a human-completed captcha for its machine-learning projects.

I look forward to the demise of the Web and its replacement with a content-addressed alternative where your views will be technologically obsolete.