Wow. Never realized there were so many methods to killing a lobster. Feeling compelled to throw my two cents in on this one. Grew up a couple of towns south of Boston and shore dinners were always a summertime favorite. We had 2 lobstermen on our street, and they never used a knife for any part of the prep work. Dropped the whole thing into a pot of boiling water or a lobster steamer (sort of like a double boiler with holes in the larger top part and a spigot on the bottom half for drawing off the broth when using it to cook steamers.) Never noticed any off-tastes from ammonia or any other stress related chemicals/hormones.
The supermarket I worked at as a kid had a steamer for cooking lobsters. Simple barrel shaped device with a door on the end and a tray that slid in. Load it up with live and kicking lobsters and turn it on. 15 minutes later you're having a tasty dinner. For what it's worth, Larsen's Market in Menemsha, Martha's Vineyard steams them this way, whole and live, fresh from the boat out back. You get your steamed lobster hot with the shell intact.
Keeping the shell intact also ensures you get all of the tamale (sic), arguably the best part of the lobster. (And the only liver I like.)
Some people say that you can stand them on their heads and when their tail curls under they are asleep and you can drop them into the pot with minimal splashing. I've tried it and it works, but totally unnecessary.
BTW, the one-clawed and clawless lobsters (Maine lobsters) are called culls in NE and are cheaper than a chicken lobster per pound, but not very popular.