Scientists A site's navigational interface is the leading edge of the visitor's experience. It facilitates human needs or thwarts them. If it is not intuitive, it is useless. In fact, some studies suggested that navigation worked better on the right. With so many sites engaging in this practice, consumers got used to it.
Bad processes encourage bad design.
There are good marketers and there are dolts in suits. Similarly, there is good user acceptance testing and there is worthless pseudo-science that promotes banality. Unfortunately, worthless pseudo-science is as easy to sell to Web agency CEOs as it is to clients. It's hard to tell until you're actually working at a Web agency whether its testing practices are informative or a shortcut to Hell. An engaged and thoughtful Web designer will develop and fight for the best navigational structure for each site, knowing that each site is unique because its content and audience are unique.