I know many people ignore it just like with all the other "I agree" check-boxes that pollute websites, but it is a breach of the Terms to sneak it onto your site or service.
Mozilla just launched a new podcast called "IRL" and in the first episode they warn people about all the creepy third-party tracking out there[1]. To listen to the podcast you have to allow third-parties to track you, and there is no privacy policy on the website to warn you.
It's actually a good podcast episode and I recommend checking it out.
[0]https://www.google.com/analytics/terms/us.html
[1]https://irlpodcast.org/ , https://twitter.com/tombrossman/status/883972350387134464