I’d be more apt to use a different analogy: it’s a well-executed e-mail scam. See, the clever people know there’s a trick to it - they just don’t reply. But many people don’t see the trick. It’s hidden. There’s obfuscation. Everything SEEMS legit! But there’s misdirection. Misleading information. It’s damn difficult to get out once you’re in, too - see, they get to tell you when you can leave. And then they make it hard. Can’t do it in the middle of something, see. Can’t do it while we’re busy. Gotta make it convenient for us if you want us to stop charging you.
Technically someone who read all the Ts & Cs and clicked their little drop down and who was on the look-out for a scam like this might be able to avoid it (my alarm bells start ringing whenever something like “the first month free”! or something like that pops up), but your “average consumer” might not be savvy enough. Even someone who WANTED to sign up for a recurring service and who later decided they didn’t want it would be hard pressed to get out of it.
They could avoid this just by making it more clear that your signing up for a service (not just ordering a pair of panties and a bra), and by making it easier to opt out of that service (it should be as easy as visiting their website and cancelling your account, and you should be able to do it at any time, though maybe they charge your card on a certain date each month so if it’s after that date, well, too late for this month).