Lord of the Rings Online, doesn't make an appearance in World of Warcraft, and an extended form is the heart of Second Life. It's player housing, and it's had a long and interesting history ever since Ultima Online pioneered the idea. There were hiccups to the approach back then, so many that some later designs have eschewed the entire idea.
Other games that use it have gone with an instancing model a la Final Fantasy XI, ensuring that there's not actual game space being taken up by unused houses. But like so many features, there are debates as to its worth. For every person who loves the idea of player-run cities in Star Wars Galaxies, there's someone who would rather see the same amount of development time going toward endgame content or system balancing.
Housing has always struggled to be an element that's meaningful beyond the cool factor of just owning a player-made house... but then again, many would argue that the cool factor itself is meaningful and why they want it. Where do you fall? Do you like the idea of player housing, are you opposed, or do you fall somewhere in the middle?