They're still tallying the figures, but Cyber Monday in 2013 is looking to be another record, with an estimated $2 billion in sales made, up 33% from last year's record-breaking performance. 

Yet the uptick in spending yesterday doesn't look like it can save Christmas for retailers this year, as the National Retail Federation says overall sales for the four-day period from Thanksgiving through Sunday fell 2.9% from last year. The number of people actually shopping may be higher (an estimated 141 million), but they're spending less, on average shelling out $407.02 compared wth the $423.55 they spent in 2012.

Moreover, we've seen this kind of story play out before, where retailers trumpet the strength of Thanksgiving sales only to see them peter out by Christmas. Beginning in 2009 we had reports of a big boost in spending at the end of November only to be disappointed afterward, and it's continued each year since. Last year, holiday retail sales were the worst they've been since 2008, despite all the hoopla over the early returns.

There's no guarantee this year's results won't turn out any different, and with weak employment numbers, higher taxes, and a still-groggy economy, the likelihood it will play out once more is great.

What might be more significant are the trends retailers can glean from how consumers shopped, particularly in the area of mobile. According to IBM Digital Analytics Benchmark, mobile devices accounted for around 30% of online traffic, a 61% increase from last year, and some retailers reported traffic was up 50% or more.

Naturally, the big winners were the usual suspects, such as (NASDAQ:AMZN), which saw a 44.3% surge in sales over 2012, and eBay (NASDAQ:EBAY), up 32.1%, but Wal-Mart (NYSE:WMT) also enjoyed a huge run, seeing more than half of the traffic on coming from mobile devices on Thanksgiving and Black Friday. Management expects the final tally for yesterday to be just as big, too.

Yet just as we're likely to see the impact of Black Friday diluted as a result of retailers pulling sales forward by opening their doors on Thanksgiving Day (or before, even, as Wal-Mart started offering its deals a week early), the significance of Cyber Monday will diminish because retailers are extending their sales beyond just that one day. Cyber Week is becoming the norm, and Wal-Mart is going so far as to offer 200 deals on its website each day through this Friday.

Because the online shopping phenomenon was essentially created as a marketing gimmick by the NRF to boost online sales, Cyber Monday doesn't hold the same tradition or affection among consumers as Black Friday does, even if it has become the biggest online shopping day of the year.

Since Cyber Monday, Cyber Week, and all its other iterations are still dwarfed by the massive $57 billion spent over the Thanksgiving holiday weekend, it suggests that if investors really want to profit, they ought to ignore trying to pick which retailer will win the Christmas shopping prize this year, and instead focus on those that ought to be best able to capitalize on mobile's proliferation.

Fool contributor Rich Duprey has no position in any stocks mentioned. The Motley Fool recommends and owns shares of and eBay. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.