Have you ever purchased something online, pressed the "Continue" button, and then, months later, discovered that you had signed yourself up for a membership program that was charging your credit card 20 bucks a month for something you had never heard of and never knew you were buying? Well, guess what: these scams are a multi-billion dollar business, they're partnered with lots of brand name sites you'd think you could trust, and they do everything they can to sign you up for their "services" without you knowing about it.
More here from Felix Salmon, but make sure your blood pressure is in good shape before you click over to read about it. Previous background about legal harrassment of a blogger who wrote about this a couple of months ago here. (Note: blood pressure warning still applies.)