As a new Bavaria owner (of an old boat), I find this forum extremely helpful, simply because it is open, so I could go and ask pre-purchase questions, and also peruse the archives to learn what ails other Bavaria owners.
I've since also taken up the BOA on their free membership offer and had a look around their forums, which seem helpful, but due to being closed are much more limited in audience and participation.
Since I'm a big fan of openness and the "donate to support what you like" model, I'd rather give some cash to Nigel for running this than cough up a mandatory membership fee.
I don't think the two are mutually exclusive though. While the forums definitely work better open, there are things a more formal organization can do better, such as organizing spare parts, group purchases (there is already a BOA shop, although it seems to be mostly selling merchandising at the moment) or events. Or perhaps get some official owners manuals online (*cough* still looking for one for my boat).
