Claim #1: "Most books sell more electronic versions than print ones anyway."
False. Most books do not sell more electronic versions than printed copies. Ebooks currently make up 6-8% of the US publishing marketplace. If ebooks outsold "most" print books in the numbers that Rushkoff is claiming, then they should have a much larger marketshare than 6-8%. Amazon has said that their Kindle ebook sales have outsold hardcover sales, but that's a very limited case study and doesn't hold true when extrapolated over all book formats and retailers.
Claim #2: "Amazon already sells more of most books than all real-world retailers combined."
False. Amazon is the biggest North American bookseller, but they do not sell more books than "all real-world retailers combined." This August 2010 article from the Nation indicated that Amazon's worldwide gross for last year is in the neighborhood of $24.5 billion, while "2008 total sales by all US bookstores were less than $17 billion." But wait--that same article also says that 75% of Amazon's sales are for non-book sales. This places Amazon's share of the US book market well shy of "more than all real-world retailers combined." In fact, some place Amazon's share of the market at just 10-15%.
One commenter on the Arthur Mag story asks the point-blank question, "Are you writing from the future, or are you just seriously deluded?" If Rushkoff is in possession of some top secret data that is being hidden from the rest of the publishing industry, then he needs to share it with the rest of us.