Civil War publishing: dilution?

Following the trail of Michael Patrick Leahy's links, I stumbled across some interesting publishing statistics.

They appear in an anonymous blog, POD-DY Mouth, where the author has been developing a dilution meme to explain what is happening to book sales figures. His particular target, if that is not too harsh a term, is the print-on-demand business:
And let's go with the average number of sales for a POD book (which I think is too low) of 75 units ... So, 50K times 75 units is 3,750,000 books. Now add on the average price of $17. That means over the past couple of years, POD has stolen just shy of $64 million dollars from New York ... And the truth is this is probably double that. The publishing industry has become incredibly diluted.
(Of related interest is a survey that shows, "... agents’ collective opinion is that a publish-on-demand book seriously hurt an author’s chance at being commercially published." Hmm.)

Back to the POD-DY, however. Our author notes:
Regarding Neilsen Bookscan's tracked sales of books for 2004 (1.2 million), here are the results:

* Of those 1.2 million, 950,000 sold fewer than 99 copies.
* Another 200,000 sold fewer than 1,000 copies.
* Only 25,000 books sold more than 5,000 copies.
* Fewer than 500 sold more than 100,000 copies.
* Only 10 books sold more than a million copies each.
* The average book in the United States sells about 500 copies.

Okay, we all know the bulk of the "99 copies and under" category came from POD publishers. What's really disturbing is that only 25,000 books sold more than 5,000 copies
I can say for certain that the "99 copies and under" in no way applies exclusively to POD. Furthermore, the lit agent calling herself "Miss Snark" says that Nielsen figures refer to ISBN number scans. Different ISBNs are assigned to the same "title" via re-issues, tape books, hardback and paper, etc. She also notes that these are hardback numbers and a partial coverage of paperback.

I think you can reach a level where generalities from numbers like these become unmanageable. Remember always that as book-buyers, we control Civil War publishing quality and quantity ... at least until the next TV or movie phenomenon floods the market with work seeking the lowest common denominator.