Investors are very cautious, more accurately put, they're probably straddling the line between prudent caution and paranoia. The growing concerns about a multi-national force becoming entangled in a region that has demonstrated continued and unrelenting civil turmoil only serves to further perpetuate the financial instability as it pertains to the S&P 500, and the DOW. Moreover, as one country goes, so does the rest of the world.
In the recent past, Greece was in financial jeopardy and although a relatively insignificant player in the global economy when you consider heavy hitters like the U.S., France, India, Brazil, China, etc…, it had immediate ramifications that resounded across the world due to the interconnectivity of economic interests and Greece's proclivity toward nationalistic pride and threats to break with the Euro.
I would expect AT LEAST that kind of impact on the world market as resources are re-allocated to quell the disturbance in Syria. These are uncertain times and uncertainty can lead to panic, especially by those who are expected to lead us economically because they tend to protect their own interests first. So in the best interest of fear-mongering, strap on your kevlar vest, continue to go to work, and just act like nothing is happening because chances are your day-to-day will not change.