In RL, land is a limited commodity. As the hoary old cliché goes, they aren't making any more. (That's not entirely true, of course; just ask the Dutch.)
Because of the limitations of the physical world and the differences between one place and another, land has value, and people buy and sell it. Some do that for a living.
SL is different. In SL, "land" is just CPU cycles and data, the work required to keep up the hardware that supports it, and the code that implements it--and those are more like Doritos than real land; they'll make more.
OpenSim will put an end to the artificial scarcity of virtual land. The only things sim owners will have to sell are services and the only thing left corresponding to proximity, i.e. access to a particular grid.
Now, the only remaining bottleneck is the asset server. I hope that work is underway to remove that limitation.