Google has been using CAPTCHA and reCAPTCHA for years now to crowdsource information from images it has found online. On the one side, you prove to Google you're a human, on the other, Google gets humans to see small images of text from a book, numbers on a house, or various objects and animals and provide OCR for the text and numbers plus logical grouping and categorization for the objects/animals.
That's the main dig that XKCD's comic today is based on. It's a CAPTCHA but it's asking the user to say if there's a stop sign, just so it can properly use that data to control its self-driving vehicle. The hidden tag is: "Crowdsourced steering" doesn't sound quite as appealing as "self-driving." Hah, so very true.
And here's your humor break of the day done. Now we shall resume our normal coverage.