Researchers with the Project for Excellence in Journalism tackle news coverage over the past four years of private security companies and they suggests that it is very much on the slim side:

Coverage of events inside Iraq, which includes the actions of U.S. troops there, was the third=biggest news story in the American media for the first quarter of 2007, according to PEJ research…. But those numbers do not include some 30,000 employees of U.S. and European-based Private Security Companies (PSCs), who work in some of Iraq’s most dangerous areas.

Unanswered Questions: Using the number of 30,000 armed contractors, the study claims that 20 percent of the foreign troops in the Iraq are private employees.
$Money$: This is one of the vexing issues. How much money is being spent on PSCs? “Financing can be difficult to track. Some PSC personnel are paid directly by the U.S. government, while others work as sub-contractors or sub-sub-contractors for other companies doing business in Iraq.”
Who’s in Charge?: ” While PSCs work alongside the U.S. military in Iraq, ultimately they serve at the discretion of the groups that hire them. Those employers may be the government, but they could also be some third party.”
How Much Media Coverage?: “Private Security Companies are a relatively unknown commodity in the mainstream media’s Iraq reportage.”
All the empirical data on media outlet coverage and accompanying narrative can be found at Private Security Companies in Iraq: A PEJ Study
The study forgot to throw these into the mix: Scandals Confront Military Security Industry and Tension and Confusion Grow Amid the “Fog of War”