Well, lots of reasons, as outlined in the report by Macro Risk Advisors (via Marketbeat) that's titled "Octagon of Uncertainty." Here are several reasons to be nervous:
--Debt implosions around the world (Portugal is on the verge of a bailout)
--Middle East continues to boil.
--Options trading on oil indicates "that prices could snap higher quickly."
--U.S. housing recent data "has been particularly alarming."
--Earnings projections might be too optimistic, especially given the rise in commodity prices.
--How will the federal government's efforts to rein in the deficit impact credit growth?
Of course, there are lots of "mights" and "coulds" in that analysis, and in the meantime investors are apparently figuring that equity markets are preferable to mattresses. The Dow was up 71 points, to close at 12,350.