What do you think of Man-Caves and She-Sheds?

The third answer option is meant to be “only fair if both man and woman in the household have a space, not fair if only one has a space”... but ran out of digits.

The concept of Man Caves and She Sheds have been gaining popularity over the last decade. I was just curious what people think of them. Are they good for households or bad? Should a house have areas that are ‘owned’ by one member and require permission to use?...

I am making the assumptions that if a wife was to have friends over she wouldn’t presume to use the man cave area to entertain them without asking her husband, and vice-versus for a man with his buddies using the she shed.. I am thinking of this in context of a space that is different then a family rec room or back yard lounge area used by the whole family.