I can answer a couple of aspects of this NavyVet. BTW Welcome back!!!
One of the chief reasons why LJ communities are where most of the BBM fanfic is found is because the forum communities had rules or restrictions about content. Davecullen.com locked its "Slash" section for members only and at one time did permit poetry and short fics, but changed that policy, in large part due to concerns over copyright and the grey area that fanfic falls into. At the same time, one of the largest archive sites, fanfiction.net, prohibited NC-17 level stories, and much of BBM fanfic is R or X - rated, explicit sexual content, which is not allowed on ff.
And unfortunately, the BBM fandom has over the past couple of years or so suffered from two major events: fandom war and cease and desists from Annie Proulx's lawyers. Some - in fact, many - authors have friends-locked their Livejournals due to quarrels and flaming by anonymous readers. I went for over a year of writing my fanfic before I got flame messages, and before I resorted to F-locking my journal I put it on blocking anonymous comments. Now I have my personal journal with my latest work f-locked, and have my earlier stories on a public archive on Livejournal, and that is mainly to prevent people I don't know but who may be following me via the internet on my user name, from tracking down my personal LJ and LJ groups. I would like to say that my misfortune in getting targeted in BBM fandom wars was a unique experience (at its height, there were five LJ sites devoted to unflattering discussion or outright flaming of my stories - I don't know of any other BBM fanfic author who had such a concentration of negative attention), however, it is not a unique experience, and many of the authors who locked their journals did so after having some sort of run-in or altercation with other members of the fandom.
I don't know whether this level of friction is typical of fandoms in general or not, because I don't have a lot of experience in other fandoms, but that is pretty much what has happened to this one, and a lot of authors have either not finished their work, deleted it, or locked it.