Investors can never predict whether the market will rise or fall on any given day, but lately, a pretty good bet has been to expect some substantial volatility in one direction or the other. For the sixth straight day, the Dow Jones Industrials (^DJI 0.06%) made a triple-digit move, with today's result being a 138-point gain that signaled investor optimism that the Federal Reserve will remain in control of the markets even after tomorrow's announcement following the Fed's latest meeting. The U.S. market remains a pocket of strength amid less exuberant markets around the world, with rioting in Brazil marking the latest uprising among populations dissatisfied with the sluggish conditions in various economies across the globe.

Only a couple of stocks posted losses today. Merck (MRK -0.11%) fell 0.1% in light of a Supreme Court decision that gave the Federal Trade Commission the power to challenge arrangements between primary-drug developers and generic-drug manufacturers that involve upfront payments in exchange for delays in releasing generic versions of name-brand drugs. Clearly, Merck and its peers have incentives to keep brand-name profits going as long as possible, and FTC challenges could reduce their ability to do so going forward.

Microsoft (MSFT -1.84%) also posted the narrowest of losses. Reports that the company will turn to Qualcomm (QCOM -1.75%) to supply some chips for new versions of its Surface RT tablet were bad news for NVIDIA, which is the existing supplier for the Surface RT, but probably didn't move Microsoft's own stock substantially. In any event, the newer Surface Pro seems like a better prospect for Microsoft going forward, given its ability to run full versions of Windows 8 programs despite its heftier price tag.

Finally, outside the Dow, MannKind (MNKD -0.49%) fell 12%, extending its losses from yesterday after completing its phase 3 trial of its Afrezza treatment for type 2 diabetes. MannKind's management couldn't identify any fundamental news affecting the stock, although later comments from CFO Matthew Pfeffer concerning whether the company might seek a partner before getting an approval decision on Afrezza from the FDA weren't sufficient to wipe out all of the stock's losses. The volatility highlights the danger of investing in small stocks with substantial speculative elements in their results.