Cyber Monday, the Monday after Thanksgiving when many people are back to work and shopping online at their desks (only during lunch breaks, we're sure), banked $730 million in online sales. On Black Friday, the day after Thanksgiving—and what used to be the biggest shopping day of the year—shoppers spent $530 million in physical stores, comScore says.

Amazon, Wal-Mart and Target were the top five most visited sites, according to comScore, which may explain why those three performed poorly in Gomez's "Merchant Madness" contest.

Gomez, an online commerce consulting firm, measured the response time, consistency and availability of 64 top e-commerce sites during four weeks in October and November, pitting retailers against each other in successive brackets similar to the NCAA's "March Madness" tournament.

Amazon, Wal-Mart and Target went down in the first round. Amazon's performance was hurt by a home page heavy with images, in-house ads and other promotions, says Matt Poepsel, Gomez's vice president of performance strategies. "Amazon made a conscious decision to develop a rich landing page because there's a lot of value they derive through the home page," Poepsel says. But the trade-off was a long download time compared to ShopNBC, which beat Amazon in the mass merchant bracket.

Both Wal-Mart and Amazon have suffered outages during crunch times. They and other retailers tried to brace IT for the current holiday shopping.

Blockbuster won Gomez's contest, beating Overstock.com in a Cyber Monday finale when more than 70 million of us shopped online. At lunch. On break. Not during work hours.