Using Amazon as an example of books available for sale might be a little bit suspect academically.
The 2317 random titles of new books available on Amazon during the fall of 2012 are charted in Figure 1 below by the decade of their original publication date. Both fiction and non-fiction titles are included. Titles now in the public domain (those published prior to 1923) constitute 72% of the total (1665/2317), while titles still under copyright constitute 28%
The above statement is problematic for me in that if the books were truly randomly selected, would these figure not be reflected in brick and mortar stores.
I have been in a lot of bookstores, both new and used and have yet to see one that books originally published 75 years ago outnumber newer works. I am sure they exist as specialty shops, but are probably few and far between.
And how many of these random books are physical books. Anyone can sell a public domain ebook on Amazon at little or no cost. At least with an paper book, there is an real cost to publish it.
Basically the gist of the article is that if the book is free more people will try and exploit it. Nothing really wrong with that any more than other forms of legal exploitation such as selling something way above market price to people to stupid to know better. Not something I would do or approve of, but not my decision to make. Caveat Emptor.
If the author of the article is referring to a truly random sample of new paper books, which I strongly doubt, than at least he has a somewhat shaky platform to stand on. If he is referring to ebooks, as 'new' simply because all ebooks can be termed 'new' or 'not used' than IMO he is just talking to hear himself and should be laughed out of town.
And saying that books disappear and are lost is contradicted several times in this paper, as many of the 1923 and earlier works came back into existence on Amazon at least in tremendous numbers according to him.