Since the beginning, Control-Alt-Backspace has been using Google Analytics, the most popular analytics service for websites. You likely visit dozens of pages that use Google Analytics every day. It’s become popular because it’s free and easy to use for webmasters.
The problem is that Google Analytics collects crazy amounts of information, far more than I would ever actually want to look at, and quite likely more than you’re comfortable with. Worse, it tracks individual users all across the Internet, via various mechanisms, recording what devices they use, their age, gender, interests, all the sites they visit, and God knows what else, and makes all this data available to anyone who uses Google Analytics. Now the users are anonymized, at least in theory – I can’t see your name and address or anything – but you probably didn’t know that most websites are helping Google build up a history of all your web activity which is then shared with advertisers.