This is something of great concern indeed. Back in medieval Europe there was this nasty practice related to mercenaries that went a little like this: An ambitious noble would borrow a bunch of money from an unscrupulous banker at high interest and use the money to fund a mercenary army. The noble would use his new army to conquer a new land. He would then steal everything he can from the inhabitants, and levy maximum taxes. He would then use this money to repay the banker. If he is successful, he may continue to conquer another land.
It was this practice that kept ordinary people in abject poverty in middle ages and kept economic growth down for hundreds of years.
If this practice is revived, there will be a lot of suffering.
This is yet another one of the screw-ups of George Bush. He recruited tens of thousands of mercenaries (hundreds of thousands by some counts) at a great cost for his Iraq and Afghanistan wars, and now these people are all over the world's problem areas looking for work.
The article mentions the possibility of mercenaries doing humanitarian work, but this is not very likely. The world's poor and weak are the ones least likely to be able to afford mercenaries.