Isn't Play world the only place money is used right now?
Actually I think I've seen a shop setup in Sky Zone as well but really it's just Play world.
Once you're able to purchase land, we may have a bit of a problem now that everyone is settled and I'm sure we'll have some people buying other peoples "already claimed" land which could be an issue.
I thought it would be good to have to separate worlds as well but even when I was adding people to the whitelist, people never played in there because they were by themselves... ?