While I wasn't familiar with the term "dark patterns," I have noticed Amazon's manipulative tactics. For example, if you have a Kindle and use the free version of their music service, they make it very easy to "accidentally" subscribe to the paid service. The button to subscribe is huge and you have to click on a tiny "No Thanks" link to avoid it. I mistakenly clicked on subscribe once and had to go out of my way to cancel to avoid being billed for another unwanted subscription.

They also make it harder and harder to access any "free" (i.e. included with Prime) video content, with more and more shows and movies being paid extras. It seems no matter how much they get out of you, they always want more.