Public awareness of the number of American military fatalities in Iraq has declined sharply since last August. Today, just 28% of adults are able to say that approximately 4,000 Americans have died in the Iraq war. As of March 10, the Department of Defense had confirmed the deaths of 3,974 U.S. military personnel in Iraq.Here is the full report PDF: 401p.pdf
In August 2007, 54% correctly identified the fatality level at that time (about 3,500 deaths). In previous polls going back to the spring of 2004, about half of respondents could correctly estimate the number of U.S. fatalities around the time of the survey.
In the current poll, more respondents underestimated than overestimated the number of fatalities. A plurality of 35% said that there have been about 3,000 troop deaths, and another 11% said there have been 2,000 deaths. Just under a quarter (23%) said the number of fatalities is closer to 5,000.