Humans, like dogs, are supposedly domesticated--civilized--socialized. Some humans are never brought into domesticity...and some revert. Reversion makes them dangerous for everyone. Our system of government was designed for use by highly civilized persons; 18th century Europeans (which includes our founding fathers--intellectually and socially European) placed a higher value on knowledge, reason, and responsibility than most do today. For a system of government like ours to survive, it must have the participation of educated people who understand a wide range of complex issues themselves (not just accept someone's talking points) and who are able to subordinate narrow personal interests to the greater good, with the prospect that others will do the same. It only works if people agree that the government is secular (not a particular religious dogma--theistic governments cannot be democratic), and agree that reason tempered with mercy governs law, and law trumps individuals. Our Founding Fathers did a good job of blending the Roman (with which they were familiar) which is very much a rule of law, with English Common Law, which is much more community based, and rejecting the Germanic heritage in law, which was very personal, even tribal. (source for that--a treatise by Dr. Lear on the difference between treason in German and Roman legal systems at the end of the Roman empire.)
A government of the people, by the people, for the people, will not survive if the people are lazy, ignorant, or stupid, any more than antelope survive if they are lazy, ignorant, or stupid. The human predators of this world, the lion and the crocodile, are always around.
So what does that have to do with mercs? If you want to use mercs, understand that they are predators and don't be prey. Don't act like prey, don't talk like prey, don't lounge around in the shallows, splashing water on each other and calling that business. Learn the business of war well enough that the mercs respect you and think twice (thrice, a dozen times) before taking you on. Notice when the mercs start encroaching on your space--taking up tasks you own military can and should do, taking over functions that give them more insight into your affairs than you should want them to have. Be aware that they're in it for profit and that--like others seeking power and money--enough is never enough.
Specifically--and this is where the current situation has me concerned--do not let the numbers of mercs, or their equipment, or their access to intel, or their freedom from legal action, exceed what your regular forces have. Why support a potential enemy force as large as your regular force, with more and better equipment, and in control of (or with access to) some or most of your intel, with a substantial fraction of its personnel being foreign nationals who have zero loyalty to you and no appreciation of your form of governmentd, so they know your secrets, your tactics, your weaponry, your training, everything about your defenses? Doesn't that seem just a tad stupid? Short-sighted?
Oh, you're sure they'll stay bought? They'd never attack you, they'd never betray you, they'd never, for any amount of money, any promises from (let's say) a faction within your own country or a powerful employer that looks to have longer-term higher pay, just step in and reorganize your government? You're really sure of that?
I suggest reading history.
Am I saying all mercs are bad people? No. Am I saying that no one should ever contemplate hiring muscle/swords/guns? No. I am saying that for a nation which claims to value personal freedom and representative form of government, overuse of mercs is extremely dangerous. Privatizing the gathering and analysis of intel is extremely dangerous, even more so in an era of publicly-traded, multi-national corporations whose various investors and subsidiaries and so on may have very different intent than shows up on the letterhead and in the public statements (guided by public relations firms) of its principals. Basic common sense would suggest that if you wan to use mercs, you don't give them all you've got, in any sense.
Guard dogs turn wolf is not a new story. I don't want it to be a news story on at 6 with pictures at 11.