Forum What is the best way to structure this forum?
 

I want to create a forum that list out several cities (goal is 10-20). Within each city, it will show different types of clubs. Within each type of clubs, it'll show the different clubs. Each club should support multiple threads. In a way, it's almost like offering a Yahoo! Group functionality for each club... Users will want a way to easily navigate to their club.

Using SF as an example, this would be a sample hierarchy:
--San Francisco
----Athletic Clubs
------Bay Club
------Club One
------The Sports Club/LA
----Golf Clubs
------California GC
------Lake Merced GC
------Marin CC
------Olympic Club
------Presidio GC
------San Francisco GC
------Sonoma CC
----Private Clubs
-------The Bohemian Club
-------The Metropolitan Club
-------Pacific-Union CLub
----Tennis Clubs
------California TC
------Golden Gate Park TC
------Golden Gateway TC
------SFTC

I only listed a few clubs per club type as examples but it's conceivable that every city has 100-200 clubs. The options suggested so far include using thread prefixes for each club or subforum for each club. Either approach will become cumbersome after just a couple cities. Another option is to do multiple instances of VB, one for each city. If that's the case, how can I provide single login across instances? Is there a discount for buying multiple instances?

I really appreciate your patience/help/advice in this!