It seems odd to me, using frozen shrimp for a shrimp boil. I don't know why you couldn't, I just envision the "real" looking shrimp, with the shells and antennae and all. I also live coastal, and while I'd be perfectly content using frozen shrimp in a regular dish, I've bought the head-on, antennae moving type shrimp from a seafood market. I think it's because when I think of a shrimp or crawfish boil, part of the fun is the big heap of steaming red-shelled delicacies that you pick apart as part of the fun of the boil. Using frozen shrimp just seems so genteel!
Of course, I also grew up in New England. There, we have lobster bakes. It's like each person getting their own gigantic crawfish.
The reason that fresh are preferred is that freezing changes the texture of shrimp flesh; it loses elasticity in the fibers, so that there is no longer that slight resistance when you bite into it. (Slight resistance is good, but of course, rubbery resistance is bad; we're not speaking of overcooked shrimp, either.) Once you add the boil seasoning, the clove in it breaks the fibers down even further. Add to that that many people mess up the timing of adding the shrimp to the pot, and sometimes boiled frozen shrimp can end up with a dry, pasty texture. It's just not very good, IMO. (Mind you, if the shrimp disappoint, I can easily make a full meal out of just the potatoes; I love those so much that I frequently make them at home without the shrimp, using liquid boil seasoning and frozen shell stock.)
I live in the midwest now, and I'll eat frozen shrimp in other dishes, but not when boiled. My DD14, who was born and raised here, is an absolute shrimp snob; she won't eat frozen if you pay her, no matter how they are prepared. Fresh, otoh, she devours. Even when she was tiny she could tell the difference; she first ate them fresh at my family's home when she was maybe 6 months old, and when I later tried to feed her frozen shrimp, she'd spit them out.
PS: While we're speaking of traditional seafood feasts, has anyone gone to a fish boil in Wisconsin? That's the mac-daddy of unusual techniques. The cooks throw kerosene on the fire when the food is done, so that the fire flashes way up and makes the pot boil over. It gets rid of the foam and oil that's on top of the water, so that it doesn't cling to the food, but the first time I saw it I wasn't expecting it, and I thought they were completely crazy.
