Yep, there are cases where it's the thing to do. Just recently I ran across a situation where a fellow bought a herd of horses that had been running out loose for God-knows-how-long.
So, he brought a wad of them up to his place and started sorting. The best he can tell is that the owner said most had been broke at one time but nothing for years afterward. So, armed with this info, he tackled these horses. Now, I gotta say that he's made of stronger stuff than I. I wouldn't have messed with them, period, but they really are nice looking horses and supposedly registered. So, really, may be worth the time to deal with them.
Anywho...he wades in and starts in on them. Most of them are so wild that to get the saddle on, he had to tie up legs/hooves and a few he had to lay them down. Not flipping them but laying them down in a controlled manner. I think I've seen CA do this but he's probably not dealing with some uber-wilds from the depths of the Oregon pastures. These are horses intent on keeping their freedom and will be damned if anyone is going to tell THEM they are to be ridden.
This fellow had to do it to get control of the horse and let the horse know who was boss. Even after sorting through 20 head, he only found FIVE that were rideable. The other 15 will head out for bucking stock. Wow!! Can you believe?
By and large, I don't like laying a horse down in such a manner but in this case I'm all for it. There is a guy on the internet named Endospink who lays horses down by turning their heads and somehow it puts the horse so at ease, he'll just drop. What I've described is nowhere near what this guy does. Actually, I like Endospink's ways and think it's fine in its place. I don't know you could get close enough to these horses to turn their heads in the first place! You'd probably end up parting your hair with a hoof!
I've noticed that people will gasp and grab their chests when you mention laying a horse down with tying a leg up but in it's place, it's a good tool to have in your tool chest.