I think there are some very serious problems with having private firms doing stuff that soldiers normally do, and among them is the secrecy and lack of accountability, and there are possibilities for abuse. But using inflammatory words like "mercenary" is not a good substitute for thinking. On its face, there is nothing particularly immoral about guarding food convoys, or government officials for that matter, which Blackwater also does, and I see nothing whatsoever immoral about taking money for doing it.

For people who ask where they can get information, today's New York Times covered the matter in considerable detail.