While filling in a form you respond to a question that tricks you into giving an answer you didn't intend. When glanced upon quickly the question appears to ask one thing, but when read carefully it asks another thing entirely.
You attempt to purchase something, but somewhere in the purchasing journey the site sneaks an additional item into your basket, often through the use of an opt-out radio button or checkbox on a prior page.
You get into a situation very easily, but then you find it is hard to get out of it (e.g. a premium subscription).
You are tricked into publicly sharing more information about yourself than you really intended to. Named after Facebook CEO Mark Zuckerberg.
The retailer makes it hard for you to compare the price of an item with another item, so you cannot make an informed decision.
The design purposefully focuses your attention on one thing in order to distract you attention from another.
You get to the last step of the checkout process, only to discover some unexpected charges have appeared, e.g. delivery charges, tax, etc.
You set out to do one thing, but a different, undesirable thing happens instead.
The act of guilting the user into opting into something. The option to decline is worded in such a way as to shame the user into compliance.
Adverts that are disguised as other kinds of content or navigation, in order to get you to click on them.
When your free trial with a service comes to an end and your credit card silently starts getting charged without any warning. In some cases this is made even worse by making it difficult to cancel the membership.
The product asks for your email or social media permissions under the pretence it will be used for a desirable outcome (e.g. finding friends), but then spams all your contacts in a message that claims to be from you.