This plugin provides an API for several "region" plugins: http://dev.bukkit.org/bukkit-plugins/flags/

Done. If Flags is installed, the default is to disallow creating shops anywhere. Flag inheritance seems to work, however if there is a "trust list" then that is used instead, regardless of the flag value, and trust lists do not inherit. May want to revisit both of these decisions later.

Added permission fancyshop.create.anywhere to bypass this, there is probably a way to do it with Flags auto permissions but this was easier.