Spurred by the growing mass-market acceptance of the Kindle e-book reader and the launch of the 800-pound Espresso print-on-demand machine, the publishing world is continuing to evolve in response to changing technologies and changing consumer preferences. What's interesting about this evolutionary change within the publishing world, according to Knowledge @ Wharton, are the psychological and social hurdles that companies like Amazon Kindle must overcome as they slowly wean consumers off physical books and on to digital e-books:

"For instance, says Joseph Turow, who studies new media as a communications professor at the University of Pennsylvania's Annenberg School, many readers are subconsciously affected by knowing that the book they see in a store was produced and shipped at significant expense by a major company -- a sign that someone who knows the business saw fit to invest in the author. "A large part of the problem is psychological," says Turow. "The fact that publishers have to pay a lot for making a book is kind of a gate to ensure that it has value.... I think the fact that there's a physical copy that has to go through hoops is part of how people judge the value of something. And that is going to be with us for a long time."

Then there's the psychological issue of how people like to "show off" their intellectual sophistication with bookcases crammed to the gills with impressive titles and thick bindings:

"Today, many people give pride of place to book collections, buying or installing vast numbers of shelves to help themselves do so. "Part of it is a symbolic kind of thing," says Wharton marketing professor Americus Reed II, who, with Williams and two other colleagues, uses Kindle as a "mini-case" in the school's core MBA marketing strategy course. "[When] you walk into somebody's house and look at their bookshelf, you can get a quick impression about a person based on the contents of the shelf. Those sorts of social signals are going to be important to people."

At the end of the day, the problem for Amazon may be that it has been "too successful," inspiring a whole raft of e-book reader imitators. For now, Amazon's breadth of titles available gives it an advantage -- something that Barnes & Noble is already working to overcome with the recent announcement of the Plastic Logic e-book reader.