when you add a portlet to the System , Plz THink in Multiple Portal scenario, Dont expect the server will have only one portal.
Google Maps is accepting only one key.
i tested in demo.liferay.net . error is comming same error is comming if i want to add key the keys for two portals.
unfinished jobs will make the people unhappy. My suggestions are to make more people use Liferay.