Evan Schuman's StorefrontBacktalk

In the middle of CyberMonday, Costco.com melted down, with its time for a full transaction soaring to 200 seconds, from a typical Costco average of about 18 seconds, according to Matt Poepsel, performance strategies VP for Web traffic tracking firm Gomez.

Although Costco fared far worse, Gomez also saw sharply slower performances from CompUSA, ToysRUs and TigerDirect, Poepsel said.

"A couple of retailers kind of fell apart today," Poepsel said in a Monday afternoon interview.

Addressing the unanswerable E-Commerce question ("When does a slowdown get considered a crash or at least that the site is frozen?"), Poepsel said the exact mark in the Web sand is unclear, but that Costco had clearly crossed it. "Very few consumers are willing to tolerate that egregious a performance," he said.

Although many sites are experiencing problems when they hand off transactions to partners—for either shipments or payment—Poepsel said the sites that had problems on Monday seemed to have the victim of their own internal issues. With Costco, for example, the problems involved activities on a secure part of its site.

For the most part, though, Gomez saw results similar to what rival Web tracking firm Keynote reported this weekend: Almost all of the major E-Commerce players are delivering fast and consistent homepage refreshes. By being able to handle the traffic spikes of major holidays on their homepage, the e-tailers have mastered the core issue.

It’s now a matter of getting the more complicated parts of those sites to just as effortlessly and to then get all partners/suppliers to do the same. As things stand today, many e-tailers "have no idea what their partners are doing," Poepsel said.

Keynote’s CyberMonday tracking also reported the Costco and ToysRUs slowdowns, but added that it saw slowdowns at Buy.com, Eddie Bauer, J Crew and Lowe’s. On the plus side, Keynote noted that Best Buy, Barnes & Noble, Dell and Overstock.com were "performing very well despite the high holiday traffic."

Both companies examine a somewhat different list of major retailers, so the fact that one retailer may appear in only one list doesn’t necessarily mean anything. TigerDirect, for example, isn’t even tracked by Keynote.

By moving the slowdowns further away from the homepage, some e-tailers have argued, the number of consumers who will grin and bear those delays gets larger. The theory is that they will then have spent time finding the items they want and will be more invested in the transaction.

"If you’ve gone through all that trouble, you’ll be less likely to ditch your product and walk out," Poepsel said, adding that it’s still a very unwise strategy. Those customers may stick it out for today’s transaction, but they’ll likely be unhappy about it and will look elsewhere for their next purchase.