After the rogue trader incident at SocGen, the investment bank I was working for required people to take a week of vacation at a time (HR would actually verify compliance). Employees would have to declare in advance that they were planning a mandatory vacation so IT could suspend their remote logins and disable their card access to the building.
In my country you normally get 28 days of vacations of which at least two weeks must be consecutive — that's by law.
Minimum vacation time per year is only 25 days though, so not everyone take all vacation at once.