An NCSU professor doing research on body armor wrote to add some insight to this post:

I am a researcher doing studies on durability of body armor materials in high temperature/humidity conditions (for the Army) and working with the Navy on physiological heat stress in different levels of body armor. The conditions in Iraq are brutal, with daytime temperatures in the summer nearing 120F (sometimes more). Operations are often conducted overnight to minimize the heat stress on the Marine or soldier. In many areas, there is little cloudiness, so the radiant heating of the troops can be much worse than the temperature alone would indicate. The human body can only cool itself by sweat evaporation above about 104F, and the extra layers of clothing dramatically reduce the evaporative cooling. Troops carry a minimum of 70 pounds of equipment in their packs. In dismounted situations (foot patrols), the safe time between rest and rehydration (a critical requirement) can be reduced to 20-30 minutes, even in the 90F temperatures experienced through much of the evening.
Adding the ceramic plates and side body armor to the situation simply makes matters worse with respect to physiological heat stress. In all protective clothing situations, the problem is balancing protection with comfort, utility and physiological load. Adding cooling capabilities to the system is being worked on, but the cost in extra load on the troops and on power supplies is a daunting challenge. Furthermore, just cooling is not enough; the condensed moisture must be removed for the body to benefit.
As noted by the Marine cited in your article, the ability of the troops to do their mission is also paramount. No armor is available to protect individuals from all ballistic threats, and their ability to move, return fire and conduct their mission may have a major role in reducing their total risk. It is fair to say that all in the industry and research community wish to provide the best possible protection, but the technological challenges to meet all the requirements are extremely difficult. Judgements and tradeoffs are necessary, and troops and commanders must make such judgements all the time.
Don Thompson
Research Associate Professor and Associate Director, Textile Protection and Comfort Center
North Carolina State University

Thanks Don. This latest controversy over body armor also reminded me to recommend Michael Yon’s dispatch on combat physics, which combines obscure facts about armor with the kind of compelling narrative Yon routinely delivers.