I also agree with Jeff and Lester here...we usually account for 4-6 acres. It all depends on the programming for the architecture, as I'm sure you realize, but you do have to consider things such as: Size of Clubhouse, Parking, Cart Storage (under the CH or it's own building), additional buildings (i.e. pro shop, dining, locker rooms can all be housed in seperate buildings), cart and pedestrian circulation (i.e. are 1, 9, 10 and 18 (and more) all at the clubhouse), event facilities (weddings, banquets, etc), service access....and so on.
And as Jeff mention, safety is a big concern...don't want a couple walking out to get their wedding photos and getting bonked on the head!