Selling the moon

Sites like moonshop.com and moonstate.com claim that you can buy a piece of the moon. How legitimate is this? Is this a good investment? Do they even have the right to sell something which isn’t theirs? Can I also claim to sell pieces of the moon, or is there a central agency that controls this?

And what happens if humans start colonizing the moon, will someone who bought some land still actually own that land, or is it worth nothing at all?

The third post in this thread explains it a little.

I’m sure this has been asked before, but this is the only thread I could see that was relevant.

Oh, and here too.