Harry Brignull has set up a Dark Patterns website to make people, designers and others alike, of the negative UX practices that are used in the UX industry. From adding things into your basket to auto-selecting options, it's a great talk that exposes what's going on and a fantastic first step to making sure that UX stays user and not business focussed. You can find the talk in the YouTube video below.
The real world equivalent of Comet adding an iPad case to your iPad order is the supermarket manager putting an organic chicken in your trolley when you aren’t looking.