Completely depends. I think lunging has it's purpose and can do great things for certain horses in certain situations. I'm a supporter of it when it's "purposeful" lunging where you're making your horse think and obey commands (change gaits, change directions, lunge over things, etc). It can be a good training technique, particularly with a disrespectful or defiant horse. If a horse won't work with you on the ground it most likely won't work with you undersaddle. What I can't stand is when people get their horse out, throw them on a line, and run them ragged for a half an hour just to get them tired before they get on. Then the horse behaves because they're tired, not because they're trained properly. UGH, big pet peeve. Don't get me wrong, when the weather's nasty and the horses haven't been turned out in a week, yeah, I'm going to throw them in the round pen a bit and let them get their bucks out before I get on! But just making them tired is putting a band aid over the problem instead of fixing it. Also, like someone mentioned, lunging (particularly the 'running around' kind) can make certain hot horses even hotter so it's not for every horse. Remember too that it puts quite a bit of wear and tear into their joints. I'm only going to do it when I need to.