An article in the Sunday New York Times describes the growing career field of usability:
SOMETIMES there is a huge disconnect between the people who make a product and the people who use it. The creator of a Web site may assume too much knowledge on the part of users, leading to confusion. Software designers may not anticipate user behavior that can unintentionally destroy an entire database. Manufacturers can make equipment that inadvertently increases the likelihood of repetitive stress injuries.
Enter the usability professional, whose work has recently developed into a solid career track, driven mostly by advancements in technology.