Of course, the anthrax mail-attacks are another form of terrorism and may have already had an incremental effect on consumer and business psychology and behavior. They will divert additional resources into provision of security rather than production of final output.
Until the last few weeks, most of the events that could materially affect the economy seemed more likely to be "bad" events damping near-term confidence and spending. But the more-rapid-than-expected progress of the war in Afghanistan reminds us of the possibility of upside surprises as well.