I also do not think sub-forums are a good idea for a variety of reasons:

1. It would mean having to check more forums in order to stay up to date on a particular airline, hotel, etc.

2. Under the current implementation it is very easy to just skim over the threads and choose those I wish to read.

3. It would result in even more non-moderator "posting police" posts declaring threads are in the wrong sub-forum.

4. It would add the additional burden on the actual moderators having to police the sub-forums and further splitting hairs when determining where a thread should reside.

5. Basically opens up a can of worms IMO.