The International Peace Operations Association, which is the trade association for mercenaries inspired by the efforts of mercenary group Executive Outcomes to end the Sierra Leone Civil War, has parted ways with Blackwater. Apparently Blackwater doesn't want to follow the group's conduct code, the "set of ethical and professional guidelines for companies in the peace and stability operations industry." Initially Blackwater, a member in good standing since 2004, agreed to be reviewed by the group after the accusations that the company killed 17 Iraqis in Baghdad last month. Now they don't want to be reviewed.
I've read a bunch of liberal books recently that touch on mercenaries and their politically threatening overtones: The End of America, Blackwater, and the Shock Doctrine.