It's a load of bollox!!
I work in retail, as deputy manager of the distribution centre and for the last six weeks we've been receiving stock purposely for Black Friday.
As others have stated it's an American phenomenon which has been over here for the last 3-4 years.....but don't believe all you see.
The "deal" prices are obviously what you buy the goods at, but the "original" prices are totally fabricated to make the customer think they are getting a better deal than they actually are.
As a previous poster used the example of the television you can get a deal of, but they've sold none of them for six months is pretty much spot on in a lot of cases - I know that some companies send one of an item to their store so they can say it "was" on sale at a certain price before it's "reduced".....this is a loophole because yes it "was" on sale at the original price, but it was deliberately left in their stockroom for weeks so nobody could buy it even if they wanted to. But, the fact it was on the premises, is a way around the issue.
End of the day it's down to individuals - if we think a price for an article is what we want to pay for it, then we will. Regardless if it's called Black Friday, Purple Wednesday or, ahem, Blue Monday.
Lastly (cos I'm on one now as Black Friday is a pain in the proverbial) as far as employers go, I receive weekly emails from all sorts of retail bods and last year there was an article about the hidden cost of Black Friday for companies.
Basically it highlighted that retailers always quote how much money goes through the tills on that day, but they fail to mention the extra labour (overtime / agency staff etc.) that is required to get all the shit on the shelves. So their actual profit isn't as large as they think.