I don’t find the explanation in the Big List, either old or new versions, entirely satisfactory.
The phrase “Black Friday” has a long, much older history. Putting it into genealogybank.com gives many hits going to at least the mid-19th century. The Trenton Evening Times of June 6, 1960 has a question-and-answer column with the question “In U.S. history, what day was called Black Friday?” The answer provided is September 24, 1869, when Jay Gould and James Fisk cornered the gold market. I have seen this event called “Black Friday” in 19th century papers as well. For an older example, the Boston Courier of February 13, 1854, quoting the Augusta (Maine) Age’s report of a senatorial election that didn’t go as the Age wished, “The deed was perpetrated on Friday--an unlucky day, at best--which will hereafter be set down in the calendar of Maine politics as ‘Black Friday.’” Another example is a 1940 film named “Black Friday” starring Boris Karloff and Bela Lugosi (and which, judging from the imdb entry, appears to be very bad). One of my favorites is an article in the Trenton Evening Times of March 5, 1974 that notes that in Iowa the salaries of all state employees above a certain level are published every year on the Friday before Thanksgiving, and that this is “known affectionately by state employees as Black Friday.” There are examples of other days of the week, e.g. “Black Thursday” of the 1939 stock market crash, but these are far fewer.
So whenever and however it was that the day after Thanksgiving came to be known as Black Friday, this was not a new coinage. It was an adaptation of a stock phrase. Any complete explanation must explain its earlier origin.
I am also not entirely convinced by the cites given. The one Dave had up previously on the Big List was specific to Philadelphia and described Black Friday as the day between Thanksgiving and the Army/Navy game. This game was a huge deal. It is still a big deal, but nothing like it used to be. It brought large numbers of visitors in from out of town for a festive, well-lubricated occasion. This is just the sort of event which locals appreciate for the increased business, while dreading for the disruption. So was this Black Friday because of the post-Thanksgiving Christmas shopping, or because of the football crowds? The earlier cite now listed is also specific to Philadelphia. It seems to me that this is a transitional phrase. “Black Friday” as we know it today is purely about the shopping, and not about any narrowly local event. A pristine example of this usage can be found in the Trenton Evening Times of November 27, 1976: “The day after Thanksgiving--some merchants call it ‘Black Friday’--marks the start of the Christmas shopping rush.”
For whatever it is worth, when I was working for WalMart in the early 1990s we used the term regularly, but it had an air of being an insider’s joke. I don’t recall hearing it is general use until later.