[Dami]

It looks out onto the vestibule, or vice versa. You can clearly see it when housemates are entering the house from with the vestibule. My guess is, that when a housemate is evicted the blind reclines and the other housemates can see the evicted housemates leaving the vestibule, or when someone else enters, but doesn't enter the main house... they'll be teased by seeing them.