dark pattern
n. A website design feature that attempts to trick a user into doing something they might not do otherwise.
Examples
2016
The hue and cry that went up in the wake of the change has apparently clued Microsoft in to the idea that there are limits to what consumers are willing to accept — and that forcing people to use an operating system by deliberately using dark patterns to exploit their understanding of how to opt out of an upgrade might just be a bad idea in the long run.
2015
Ever subscribed to a mailing list by mistake? Booked travel insurance without noticing? Then you've fallen for a Dark Pattern.
—Natalie Nahai, “Dark Patterns and Ada Lovelace — Tech Weekly podcast,” The Guardian, October 22, 2015
2014
Ultimately, consumers will find the benefits of providing anonymous data in exchange for valuable experiences a lot less irritating than page-overs, endless commercial breaks and dark patterns in digital user experiences attempting to trap them into an acquisition funnel.
—Dave Meeker, “How Well Do You Know Your Consumer?,” Adweek, August 12, 2014
2010 (earliest)
However, there's another kind of bad design pattern, one that's been crafted with great attention to detail, and a solid understanding of human psychology, to trick users into do things they wouldn't otherwise have done. This is the dark side of design, and since these kind of design patterns don’t have a name, I’m proposing we start calling them Dark Patterns.
—Harry Brignull, “Dark Patterns: dirty tricks designers use to make people do stuff,” 90 Percent of Everything, July 08, 2010
Notes
In website development, a design pattern is a kind of template or recipe for a common element (such as a shopping cart) or experience (such as entering a password). Design patterns are usually helpful because they enable designers to avoid reinventing website interface features that arise constantly, and they enable users to avoid relearning how to use those features. Since there is often a fair amount of psychology underying these patterns, it should come as no surprise that the world's design-focused sociopaths have twisted this psychology to their nefarious ends to produce dark patterns. See the Dark Patterns site for lots of interesting (and, sadly, all-too familiar) examples.