Errr, nobody in that other thread suggested that ownership of the parks would be turned over to a private business, just that the operations would be privatized. A hotel chain running the lodges at Yellowstone for example.
It certainly doesn't mean "roller coasters at the Grand Canyon".
A private company(s) already does run the hotels, and other concessions, in Yellowstone and other parks, monuments and units of the National Park System. Depending on what services are considered necessary in a particular park, the concessions might include food, gas, lodging of various different types, guided rafting trips, guided horseback trips, packing, etc. The government is not doing all those things; they are managing the concessions.
There has been a great deal of controversy in the past over the amount of $$ these concessions pay (or don't pay) to the NPS for their concession contracts. In the big parks, they've raked in the big bucks while paying a paltry fee in the past.
As far as privatizing the national parks and associated units, I think it's a bad idea and at odds with the Mission Statement in the 1916 Organic Act: "To conserve the scenery, and the natural and biological processes and the wildlife therein; and to provide for the enjoyment of the same, in such manner and by such means as to leave them unimpaired for future generations." There's also been a lot of controversy over that statement, and which part of it should be emphasized as there's some obvious conflict in there, but the most recent interpretation emphasizes the conservation aspect, using good science.
That being said, the parks & monuments have not been particularly well managed in the past. They are extremely political; political appointees run many of the larger units and the Secretary of the Interior and Director of the NPS are political appointees. The NPS has functioned on the premise that the rangers are "paid in sunsets" and if someone gets sick of living in a remote area in substandard housing for which they're paying through the nose, well, there's someone else eager to take their place. Lately that hasn't been the case; people aren't willing to give up high-speed internet, TV, cell phone service, etc., to work for a government agency. Morale among park staff has consistently been among the lowest in the federal agencies (I can probably find those studies if anyone is interested), park law enforcement rangers have been the most frequently assaulted of all federal officers (I can also find that cite) and good science has often taken a back seat to political expediency.
That doesn't mean that private companies would necessarily run the parks any better. But the current system leaves a lot to be desired, and that's why the idea of privatizing them isn't simply dismissed as ridiculous and keeps on coming back up.
There's a public site called
www.nationalparkstraveler.com that keeps pretty good tabs on what's going on in the NPS, including some of the controversies (also see
www.honestchief.com).
By the way, there are 396 units of the national park system; only 50 of them are called "parks". All of them, however, are managed under the same system and controlled by the same set of regulations, and many of the monuments, etc. are just as spectacular as some of the parks.