I remember reading several years ago that a high percentage of the civilian casualties of the Pearl Harbor attack were caused by US military anti-aircraft fire that went astray. It's entirely possible the same thing happened in Baghdad given the number of shells and missiles they've been firing into the air. Most shells are set to explode at a set altitude and most SAMs will detonate if they miss, but there's always room for failure.

That also applies to our weapons. Reportedly, one or two cruise missiles went into Iran and perhaps even Turkey. Still, if we know that X number of planes released Y number of weapons in a given area, then find evidence of X * Y impacts in the battle damage assessment, we can be pretty sure that none of our weapons went astray in a given attack. As for the Baghdad incident, I saw the craters in news footage and they just didn't look big enough to be caused by a cruise missile, much less the larger JDAMS or other weapons likely to have been dropped by our side.

Then again, there's always the possibility that the shells (or whatever) that hit the marketplaces were fired intentionally by the Iraqis to stir up international support. The British have reported this week of Iraqis firing mortars and machine guns into Basra. I wouldn't put it past them.