The downgrade adds a few wrinkles for companies deciding where to put excess cash --- so plentiful in many corporate coffers these days. To be sure, most companies' investment policies don't specifically require U.S. Treasuries to meet a certain rating, Pan says. This should reduce companies' need to sell some investments in order to ensure they remain within their investment policies, he adds. "We don't foresee forced sales."

At the same time, companies may want to reevaluate their investment policies, many of which were written for calmer periods, Carfang adds. "They presumed that government securities would not be rated triple-A."

That's one step that Craig Creaturo, CFO and treasurer with II-VI, Incorporated, a $500 million producer of crystalline compounds for use in laser optics and other applications, will be taking. The policy, which allows for investments in U.S. government obligations without regard to credit rating "was drafted with the view toward the U.S. always being AAA rated."

Liquidity and solid asset quality, while always important, now are key considerations when investing, given that that the market itself has gotten riskier, Carfang says. "The proper position two months ago is no longer proper today."