Allocating Land

I think it would be a fantasic idea if we could allocate a block of land to a user. I used to use second life as a place to build and meet up. There you could draw a square on the land and allocate it to a user so they could only build within that area. This was perfect for those of us who were building cities etc. I am making a city in Minecraft at the moment and would love it if I could do the same here so they have to build in land that won't be used for roads etc.

A user could obviously have more than one parcel of land allocated to them. In SL you would charge for that land but I don't think that would be appropriate in Minecraft. I just think it would be a useful tool for getting people to contribute to my city without the risk of them destroying other people's buildings, roads and street furnature.