Well since my previous post was deleted for some unknown reason by the overzealous moderation team that apparently has taken command of this forum, allow me to restate my views in a much more concise manner.
1) - If you lose an arm, you have no way to activate your laser ... unless you're leaving it "clicked on" and then lose your arm, in which case you are sending a tracking beacon to everyone around as to your current location.
2) - Using a green laser for "intimidation" to avoid a shoot is the same philosophy that "racking a shotgun sends them running" or "warning shots let them know I'm not fooling around" or "using birdshot lets me hurt them without the liability of killing them". In all cases, flawed logic and junk science are the culprits, yet all three have strong proponents that actually think it's a good idea.
3) - A light is infinitely more useful than a laser on a shotgun. Proper usage and light discipline are key. You don't just "click" the light on and then go roving ... that makes you a lighthouse and thus a target. Short bursts of light to illuminate areas, followed by movement away from that position as lights have a way of attracting bullets from bad guys.
4) - I'm not sold on the idea of any optic being needed for a shotgun for HD, let alone a green laser with a visible beam. I'm not speaking out of inexperience, I spent $800 or so and bought the surefire green laser back in the day and used it for a bit with a LMT AR ... and I promptly sold it. It was a toy / novelty / gimmick at best, at worst it was a bullet magnet / unnecessary weight / unnecessary opportunity cost.
Now, that being said ... lasers certainly have their use in warfare and in self defense. IR lasers are a game changer when paired with night vision and air support, and red lasers on CCW guns can greatly increase your chances of getting rounds on target. I just don't think they are appropriate or necessary for a HD shotgun at point blank range ... and if you're using your shotgun at 100 yards, you're doing it wrong.