Eric Schaffer explains why usability is no longer enough.

httpv://www.youtube.com/watch?v=bminUlAu47Q

Traditional usability practices focus on creating efficient sites that are simple and easy to use. Thus, usability deals with the “can do” aspect of design (i.e., can users find information, understand content, or complete a task?). But just because a site is easy to use doesn’t mean it will engage consumers and meet business goals.

http://beyondusability.humanfactors.com/