Librarians make good usability advocates. The science of usability engineering is developing a prominence as it requires specialists with a sound knowledge of the way readers interact with a body of knowledge. As documents online become longer, ease of information discovery becomes more and more important for the retrieval of the information. I consider myself to have the skills of a usability engineer through my association with librarianship. Librarianship is more about accessibility of information these days than it is with the guardianship of knowledge.
Usability is all about making information discoverable.
Librarians have the ability to contribute to the development of usability standards by thoughtfully developing and building on traditional information techniques. For example, I am currently lobbying the concept of a digital verso as a standard for onscreen publishing. The verso has seemingly been forgotten in the race to publish onscreen, I think because the people doing the publishing have not been aware of it's value. When people publish they usually think of the content - the chapters and the text. The verso - which connects the content to the larger information world and contains things like the isbn, publishing details and copyright information, is just as important to an onscreen document as it is to a printed one.