The recent mess with Blackwater has—understandably—riled some tempers, fueled some angry debates, etc., the word “mercenary” often slung about in no uncertain terms.
No uncertain terms which have often remained somewhat uncertain on account of no one really bothering to seriously puzzle over what meaning, exactly, mercenary has in the context of the conflict in Iraq.
(e.g., Using mercenaries is evil! No, it’s pragmatic! etc.)
Mark A. R. Kleiman writes an excellent, thoughtful post on What’s wrong with mercenaries?, and you should go read it.