We might not like to admit it but deception is deeply entwined with life on this planet. Insects evolved to use it, animals employ it in their behavior, and of course, we humans use it to manipulate, control, and profit from each other. With this in mind it’s no surprise that deception appears in various guises in user interfaces on the web today. What is surprising, though, is that up until recently it was something web designers never talked about. There was no terminology, no design patterns, and no real recognition of it as a phenomenon at all. If it wasn’t a taboo it certainly felt like one.

If we put aside our moral quibbles let’s put ourselves in the shoes of an evil web designer for a moment. How can we take advantage of our customers in the most effective manner? First off, subtlety is our friend. For example, if our site is going to hit users with hidden costs in the checkout process, we’ll be more effective if we add relatively small costs. If we add $100 to a $20 purchase, the customer will most likely notice and drop out. We’d be much better off adding just a few dollars as some sort of “order processing fee.” Even if customers notice this, they probably won’t bother dropping out as the cost is too small to justify going through the checkout process on another site. This is why deceptive user interfaces are so common on the web—in isolation they’re usually so small that each one is barely annoying enough for people to do anything about them.

https://alistapart.com/article/dark-patterns-deception-vs-honesty-in-ui-design/