Pluses and Minuses

Sean McFate writes about mercenary military forces for The New York Times. As he notes, mercs are cheaper.

Mercenaries are less expensive than standing armies, just like renting a car is cheaper than owning one. (snip) Blackwater cost 10 percent less than a comparable army unit in wartime Iraq, and a private force costs nothing in peacetime because its contract can be terminated. 

When not employed doing something good, unemployed professional soldiers sometime find work doing something not-so-good. They have been recruited to overthrow third world governments, or guard drug kingpins, for example.