Shoppers are expected to spend more than £3 billion by the end of Cyber Monday despite a "muted" Black Friday on the high street prompting suggestions the American phenomenon has already peaked in the UK.
Retail giant Amazon reported record figures on Friday, with more than 7.4 million items ordered, leading to its biggest sales day ever in the UK.
But the predicted in-store chaos of last year failed to materialise, with one expert claiming Friday's discount bonanza was "like signing a death warrant" for retailers and more than a quarter of high street shops had decided not to take part.
Shopper traffic on Black Friday fell by 4.05% compared to last year, according to retail experts FootFall.
The decline is set to continue over the weekend, with only Saturday predicted to see a marginal rise in shopper traffic (+0.5%), before falling once again on Sunday (-2%) and Cyber Monday (-0.5%).
Analysts have forecast that the flood of customers snapping up deals online could lead to a total four-day spend of £3.2 billion.
Retail expert Richard Hyman said his research had shown 26% of high street stores had opted out of Black Friday.
"Last year I think the industry embraced Black Friday with tremendous enthusiasm and dived in," the consumer analyst said.
"In the months that followed it was able to evaluate the consequences which, for most, were pretty dire. This year it's been more muted.
"There is shopper and retailer fatigue. Everyone is saying it's going online and I think that's going to be true in some ways. But it's going to wreak the same economic damage.
"It's like signing a death warrant. I think we've seen the peak of it. In private, many retail CEOs wish they could wave a magic wand and do away with it."
Another expert said the weekend of discounting looks to be moving towards a four-week sales season all the way to Christmas.
Jon Copestake, of the Economist Intelligence Unit, told the Daily Telegraph: "What we are starting to see is Black Friday, Cyber Monday and Super Saturday all roll into one in a sales season that lasts several weeks in the run-up to Christmas."
Some companies struggled to keep their websites up and running on Black Friday, traditionally held to coincide with the end of the American holiday of Thanksgiving, as huge numbers of people logged on to try to get the best deals.
The John Lewis website went down at around 3.20pm and when one disgruntled customer called up to confirm an order lost online, they were told the retailer was unable to take any orders and to call back in an hour.
One IT analyst estimated the company could have lost £2.8 million.
Shoppers using the Argos, Tesco, Boots, River Island and Debenhams websites also reported problems.