On two projects I've had the request to limit the languages visible to certain regional users. The use case is:
Regional group North America - can change field values of English, US English and Spanish
Regional group Europe - can change field values of English, French, German, UK English.
So we set up the 5 additional languages (English is the default language created during install).
On one project this was not a hard requirement, however I've another client which really wants to block the visibility of the European languages if the user is in the North America region (both to cut down the amount of screen clutter, restrict visibility and prevent mistakes/support calls. Currently it is possible to carry out an amount of translation work only to find out the wrong language was selected and the record cannot be saved)
Customer support service by UserEcho