I haven't been in a gigging boat since headlights left the scene. I have been very close to boats with these lights, when we we're leaving and they were starting, and I can tell you that in about 4-5 feet of water and 15-20 feet away I could see every rock on the bottom. Yes I'm speculating about how deep they can reach and about hunting cover where other species hide, but I don't see them finding a lot of bass in the open because its not where they are as a norm.
I'm in the same camp as Al, and have been for years, that it only takes a few to cause havoc. It was reported, I never did confirm absolutely, that several years ago they hit the Niangua pretty hard and confiscated several boats over game fish being gigged. I don't know who they were, but I do know there were some in the area that had no qualms about gigging game fish and it wasn't any secret.
It seem to depend a lot on the rivers and the amount of activity. I've never heard of any trouble on the James, that doesn't mean there hasn't been some, and if true I suspect its because of the heavy traffic. A lot of boats will likely make it too risky, for fear those giggers who don't want the attention will turn on them. That's also a guess, but its also part of my belief that's its a small number of people and they should be that much easier to stop.