Marco,
When I lived on the Mainland, I belonged to the local fly fishing clubs. The clubs were great, and had a nominal membership fee to help defray costs.
I see FAOL as something akin to a fly fishing club. I'm sure there are a lot of costs we, as users, are unaware of; i.e., web hosting, hardware, etc. I get the impression that bulletin board type forum sites like this one are not big money-makers. So, I don't think they fit the "normal" business model.
Anyway, just my personal opinion....which I recognize. It may be that other sites like this one may someday need to look to revenue sources other than advertising. It may be that, as a group, members of forums in this sport may not be big supporters of the companies that do advertise in such forums - thus diminishing revenues to the site owner(s).
We shall see what the future determines.