Break down various regions into Sub-Forums for Get-Togethers, Rides, LBS's, Trails, Events, etc so that BF members can hook up.
I subscribe to some other boards that utilize this and it seems to work out nicely.
USA-New England/Mid-Atlantic/South East/Mid West/etc (**Added bonus... we'd get to see how many dolts don't know their geography example... Someone posts in Mid West that they are looking for a good LBS and folks respond with shops in Chicago, Michigan and Indiana only to find out that the original post came from someone looking for a good LBS in the Mid West area of their state which happens to also be Texas )
or just simply go with USA and the rest of the world (until folks from other places express enough interest to justify starting a new locale like Asia or Oz).
Try the idea for a few months and lose the ones that have little to no activity going on.
All just an idea...