Following the ad blocker crackdown, YouTube is explicitly going after third-party — often mobile — apps that let viewers skip advertising. YouTube announced today that it is “strengthening our enforcement on third-party apps that violate YouTube’s Terms of Service, specifically ad-blocking apps.” Users will see a “The following content is not available on this app” error message or experience “buffering issues” when they try to play content though those alternative clients. We want to emphasize ...