*On Mercs and PMCs*
Too lazy to do a post on the French rejection of the EU Constituion in their referendum, so I'm cribbing a reply I made to a post on the Young Republic.
Mercenary groups have been around for quite some time, the most famous and feared of which were probably the Swiss Mercs who were barred by the Vactican (I think) from selling their services outside of Switzerland. The entire history of warfare (particular on continental Europe) was one of mercenary warfare. See in particular their use by the Holy Roman Empire. At any rate, whichever position you wish to take, there's probably going to be sufficient examples from this period.
Fast forward to today, what exactly do we mean by Mercenaries?
a. We have Private Military Contractors (PMCs) who provide a whole host of services, from Sandline International who will provide actual ex-SAS/Special Ops personnel to hunt down fugitives or to fight on an actual front (well...actually Sierre Leone is one of those 'modern' wars which blur the lines between war zones and insurgent hit peace-keeping zones).
b. And then you have those who provide personnel training and consultation and mostly bodyguard stuff (Executive Outcomes, since disbanded, fought in SL and Angola but provided mostly combat support roles in Iraq).
c. And then there are also groups like Halliburton (and particularly its subsidiary Kellog, Brown & Root) who don't carry weapons but does almost everything else which the media lumps together with PMCs. For a description, see their own website here
For an extensive treatment of PMCs in Iraq, see here.
Considering the fact that most nations find them politically expident to carry out policies that might otherwise be troublesome if linked to them (say one of your MNCs are operating in a territory which you have otherwised deemed an enemy and hence if a civil war breaks out you really can't send in the military), I think it would be safe to assume that they are sufficient reliable. If so, I think it is not entirely inconceivable that for an army that wishes to conserve its resources in terms of armed personnel services, it could outsource things like training or translators or even sentry personnel duties in a war zone but away from the frontline, e.g. protection of oil pipelines and infrastructure in Kuwait or even in Iraq as the armed forces push on.
So while I can conceed the theoretical point that perhaps money and a contract can't beat (when it is genuine) things like Loyalty and Duty, nevertheless it is worth noting that there seems to be a deafening silence for substantiation on this point. My personal feel is that history has developed a pretty robust code of conduct for these people. Furthermore, these mercs are no longer 2nd sons with no inheiritance or people with criminal records but honourably discharged ex-military personnel (some poached even when in service which breeds it own problems for the military that trained them in the beginning). As such, considering how competitive this industry is, their reputation and continual survival is on the line with every contract they make and every mission they undertake.
However, it is also true that they are shrewd operators. After all, put yourself in their shoes, do you really want to be forced to fight against overwhelming odds to the last person? So within their contracts are clauses that allow them to scoot when certain criterias are met. Of course in the mess that is war, anything could happen after all.
So yes, while there probably is nothing stopping them from running with military secrets once the war is over (but why entrust to them anyway?) but like almost every double agent, the very success of their operations made them immediate suspect by their new political masters. Furthermore, as far as I can tell, most of them PMC have links to particular countries or group of countries so I think this makes such a danger more remote.
The real problem is really with the nebulousness of their legal status. After all, they aren't really soldiers as we understand them. Although it could be argued that they do fulfill the criterias under the Geneva Convention and hence ought to be entitled to POW status is capture. I pretty much think that this is a very academic problem. After all they do have a very long history and most armies have ways of dealing with them. Besides since they aren't realy affiliated with anyone, they tend to get ransomed back to their companies more than anything else. However, in today's war where employees of private firms can get killed and executed because they are perceived to be aiding the enemy, that convention might get turned on its head.
*Mr Fluffy ignores this entire post magnificantly. He has opted to built his entire army of Minions of Twilight rather than do the crass thing of hiring mercs. As a result he has swiftly crushed the opposition in his quest to annex the tropical island. As of now, he has begun remodeling his Imperial Palace in his image. Mr Fluffy is also soliciting ideas for names to rename his Imperial Conquest Annexed Territory*