Labeled as domain in Domain Appraisal, started by Karolis Sto, Mar 11, 2016
Personally I'm not too sure that the domain name links with the extension as 'world' and 'earth' have separate meanings (world as in where we live and earth relating to the name of the planet)
If the domain was map.earth then possibly better - but even better is world.map - with the .map domain making an appearance in 2016 apparently.
I don't see value, because the whole domain name is redundant.
Also world map and national flag type of websites were made from the infancy of the internet and its a well entrench internet space.
There really isn't endusers wanting to pay premiums of world map development.
And the plural (which is still logical) can be reg for $18
Feels regfee without development.
Separate names with a comma.