When Player Housing was first introduced not all neighbourhoods were in the game to start with. As all of a particular type of house got bought up in all the available neighbourhoods on a server the server would spawn another new neighbourhood.
I would assume that with the new foreclosure system that this has been reintroduced and the completely empty neighbourhoods have despawned until they are needed again.
[center][url=http://forums.lotro.com/showthread.php?18699-How-to-get-help-on-the-Tech-Forums-and-how-to-contact-Turbine][color=gold]How to get help on the Tech Forums and how to contact Turbine[/color][/url]
[color=green]Please reply to the topic or PM me if a solution I posted works for you: The more data I can gather the better I can help.[/color][/center]