According to businessweek.com: Cyber Monday is only the 12th busiest online shopping day of the year, and the term was coined just last week by Shop.org, a retailers' association looking to create a little buzz around online buying.
P.S. I did a bit of cyber shopping on Monday, myself. :)
Update: Dvorak Uncensored | Online sales take off on ‘Cyber Monday’ "American shoppers, intent on skipping crowded stores and 6 a.m. squabbles over the last bargain laptop, spent 26 percent more money online over the Thanksgiving weekend than they did in 2004, according to market-research figures." The way I read that is sales, continued, on Cyber Monday. There is an hysterical comic at Dvorak's blog, check it out ;)