Usability (and UX, as a wider thematic area) has lately been gaining awareness by the Web community. But while most of us are using it to improving our users' experience on our websites, some are using the findings of usability research and interaction design to trick the users as a mean to improve their profit.
As a two-edged sword, you may be tempted to use anti-patterns to improve your profits, but the main motivation is to teach you, as a Internet user, to identify and avoid them, and as a Web designer/developer to introduce inadvertently any kind of anti-pattern into your products or sites.