Today we got an interesting report about the own.maps feature on gmaps.
If you create a private map at own maps You're able to invite others.
But if you like to remove someone from list "collaborators" it doesn't work. He will be able to view and edit this map and he will also be shown at list "collaborators" after a short time/browser refresh.
So removing someone from Collaborators-list doesn't work as it should do.
Create a new map and import the old data via URL. Just copy url from "View in Google Earth" from original map and insert into URL-field.