I always encounter a "random" stop-and-solve-me-a-visual-puzzle when visiting an Australian forum related to SOHO networking equipment. According to the description on the challenge page, "completing the CAPTCHA proves you are a human and gives you temporary access to the web property". Thank you, Cf, I guess?

(To be fair, consecutive requests don't get this treatment, just the one in which I jump there from eg. a search result.)