I joined this forum maybe 6 months ago and quickly found out who the "regulars" are. Now, it seems to me, those "regulars" are not so regular anymore.
Replace '6 months' with 6 years...and you'll be echoing a common thought.
Internet forums, it seems, have a certain life cycle. They start off small, and if they succeed, they create a nice (probably little) community. As they grow bigger, that sense of community tends to get muddled and sometimes lost. The 'regulars' that you remember, become a smaller and smaller percentage of the group.
Of course, some people go and more people turn up. Old regulars fade away and new ones rise to the forefront. If a forum is to be successful in the long term, it needs a good influx of fresh blood.
This forum in particular, has always been a magnet for new/beginner photographers. I'm not sure of the stats, but we probably get a hundreds of new members every month. That really drives the overall direction of the forum. So while we do have a good base of professional photographers and highly knowledgeable people, it seems that the longer a member is here, the less 'new information' they will pick up on a day to day basis. In other words, as people grow with their photography, they will essential out grow this forum.
But of course, those who do stick around, likely do so because of the sense of community that still exists...even if it's not the same as the remember from years gone by.