After four straight triple-digit swing days, the Dow Jones Industrial Average (DJINDICES:^DJI) contented itself with a modest advance Tuesday -- although today's session was still rife with volatility. The Dow rallied 200 points from midday lows to finish in the black, as rising inflation inspired hopes that the U.S. economy is gaining momentum and a rally in Twitter stock fueled a tech comeback. The only struggling sector was consumer services, with Wal-Mart Stores (NYSE:WMT) and J.C. Penney (OTC:JCPN.Q) lagging notably as Sears Holdings (NASDAQ:SHLDQ) held its own. After an up-and-down day, the Dow finished up 89 points, or 0.6%, to end at 16,262. 

Wal-Mart's 0.7% stumble was almost good enough to make it the worst performer in the Dow, an unceremonious honor that went to Verizon instead. A 0.7% decline isn't anything for investors to lose sleep over, but clearly some shareholders were perturbed by research firm William Blair's newly bearish outlook on the retailer. Although the core thesis -- that Wal-Mart's massive size will hold back growth -- is rather lame and obvious, analysts also cited a more worrisome threat: e-commerce. Developing its online presence was a major part of the company's holiday strategy, and it still has plenty of developing left. 

Source: J.C. Penney website.

While everyone and his mother has known about e-commerce for years, it's still a sobering threat to conventional retail. The phrase "adapt or die" remains as relevant as ever, although for retailers being late to adapt to an online model may be just as damning. J.C. Penney, which shed 4.7% on Tuesday, did a fine job embracing e-commerce in the fourth quarter, with online sales jumping 26% year over year. Still, sales through its website accounted for just 10% of overall sales, highlighting how reliant J.C. Penney still is on its physical locations.

Stock market performance -- especially intraday performance -- too often belies the strength of the business behind the ticker symbol. Shares of Sears, for instance, surged 5.9% today, even though the company is hemorrhaging cash and spun off its Lands' End brand for some extra loot earlier this month. Whether the decision proves to be a shrewd financial move or a guarantee of its own demise remains to be seen, but Sears' slumping sales probably won't reverse course anytime soon. That said, one should always give praise where praise is due, and with Sears concentrating capital expenditures on online and mobile shopping capabilities, the company is trying its best to adapt rather than die.