I really do believe the comparatively small membership here is a direct result of the limited forum category range (i.e - one).
I'm not clear, either, on the comment that it would take too long switching from one to another - surely no longer than switching from one thread to another? How do you manage on the Creative Cow forum with its plethora of categories (http://forums.creativecow.net/forums.php).
I rather imagine that, anyone solely interested in, say Adobe Premiere, will make that their target destination for each visit (no switching necessary unless they wanted to browse) - and they would have the knowledge that all the posts therein are focussed on their topic of interest. That isn't the case now
How can that be worse than having to search through every topic heading to find anything related to their particular interest? I suggest it takes far longer to search through the posts for a heading of interest than to simply switch categories.
Sorry Michael, fine name (!

Actually the Creative Cow link shows how advertisements could look for 'non-IAC members. Not too bad at all, IMO. Better without, perhaps - but maybe there ought to be an option to 'See the current advertising...'. Who knows - there may be something of interest amongs all the offers!!