One thing that's been true about the U.S. stock market for years now is this: it's hard to keep it down. After three consecutive days of declines, including a couple of 100-plus point drops for the Dow Jones Industrials (^DJI 1.18%), investors decided they'd had enough of the doom and gloom. Accentuating the positive aspects of optimistic economic data rather than worrying about the potential for the Fed to slam on the brakes with its bond buying, the broader markets all rose between 1% and 1.5%.

But Microsoft (MSFT 2.22%) missed the party, falling 0.8%. The company announced that it would join mobile up-and-comer Samsung in implementing an in-store shop presence within Best Buy (BBY 2.80%) locations. It's obvious that these deals are essential for Best Buy's success, as the big-box retailer slims down its massive store locations and emphasizes mobile products to a much greater extent. But for Microsoft, the move raises questions about whether the company plans to follow through with its own proprietary retail-store concept, or will rely on these in-store specialty shops for the bulk of its bricks-and-mortar strategy. In any event, today's losses only give back a small portion of the big gains the stock has had in recent months, as investors become more confident about Microsoft's overall future.

The other Dow loser today was DuPont (DD), which declined by two-thirds of a percent after issuing a profit warning this morning. Investors have gotten used to retailers blaming bad results on the weather, but DuPont also cited a wet planting season as holding back profits in its key agricultural segment. Given that the ag business makes up almost half of DuPont's overall revenue, sensitivity to weather conditions has a material impact on the overall business. Nevertheless, the big question is whether those revenues will simply get pushed back into the third quarter, or whether they'll be lost for good Given DuPont's guidance that full-year operating earnings would come in at the low end of its forecast range, the answer doesn't look good for shareholders.

Finally, beyond the Dow, Barnes & Noble (BKS) fell 9%. Earlier this week, the company reportedly stopped supporting the stand-alone versions of its Nook reader software, instead diverting Nook users to web-based versions. With some of Barnes & Noble's e-book offerings not supported by the web-based version, however, the move seems to indicate that the company no longer sees e-books as an important part of its overall business strategy. Investors don't like that assessment, as today's drop adds on to a substantial decline yesterday, as well, boding ill for the company's future prospects.