What I don't understand, in the context of modern architecture, is the complete breakdown of the traditional distinction between public and private space. It's one of the things I dislike about the open floor plan concept.
For me, open floor plans have always been about facilitating togetherness. In the evening, one of us is usually cooking or cleaning in the kitchen while the other in relaxing in the living/dining room. If those are completely separate spaces, it cuts off a significant amount of family socializing. Plus, in a closed off kitchen I feel like I'm just there as a servant to cook and clean in the dungeon. In the open floor, I'm chatting, watching the same shows as everyone else, casually minding the cooking, and chiming in for help when I need it.
Obviously these are common feelings since it's pretty standard to see a modified traditional floorplan with space for a TV and dining nook in the kitchen. Personally I'd much rather have just one living room and dining room and just let it all flow together. I guess I just don't care if my guests see the dirty pots and pans from the dinner I cooked them.
I suffer from an open floor plan in my house. At some point in the future I plan to close off the kitchen, workroom, and laundry areas, which are contiguous and attached to the back entrance, so that there's more peace and quiet. All I'll have to do is wall off the area above the kitchen counter so that it's not visible from the living room. That way, all I have to do to spare my guests the sight of dinner preparations in progress (or unwashed dishes afterwards) is to turn off the light in the kitchen. The public areas (living and dining room, halls, foyer, and access to a bathroom) are also contiguous, which is good for entertaining.
Open floor plan + high ceiling = noise. It's fine if you live alone, but if you have two or more adults it becomes a problem unless you want to live Abbey-Of-Theleme style in which everybody participates in every activity, all the time. That's how it has to be in the public parts of the house. Nobody can study or read in the living room with pots and pans clanging in the kitchen, and the only way to have a private conversation is to withdraw to one of the private rooms in the house. My daughter may eventually have a television, but if so it's got to be in her room. I wouldn't want it in the living or dining area. Her (bleeping) phone and tablet are already enough of a distraction during mealtimes. I do not care to compete with even one more electronic gadget.
When I have guests, the purpose behind entertaining them in my home (as opposed to a restaurant) is because we want to interact with each other. We want to socialize without having to shout over background noise. Some of my friends or family are elderly and have hearing aids. Loud music, electronic yammering, and high levels of background noise cause them to be unable to hear what is being said by the person across from them at the table. That's what makes it difficult or even impossible to dine with, say, my parents in most mainstream restaurants. Everything has to be noisy, clanging, and echoing as much as possible in order to be "hip".
I do like one aspect of the open floor plan: it makes it easier for my mobility impaired friends to get around. My house is wheelchair friendly since it's all on one floor.