Piotr,
I think I mostly agree with you. Personally I didnt invested too much time in expertise -- I created one group (devoted to the mushrooms) and stepped back to watch the concequences. Probably it will take solid time, sufficient amounts of work and promotion, so that something will mature from it. I have time to wait, but I really dont have energy to invest in the efforts. And it looks like other users share my position.
Why use it, if we have tribes already?
Your point about content planting not being possible to several communities at once, is 150%, bingo! Giving the 1st tag to some nameless stuff (hive ##### - what does it mean? nothing!) is discouraging also pretty much.
I've invited to my fungi-dedicated community a dozen of users, the result is about zero. Seems like my friends share the lack of intrest to it. Well, it looks like that. Maybe it has some energy and benefits in potential - like a natural plant's seed... I will give it time, lets see how it will turn out, when more people check it and use to live with it. Give it time, dont try to calculate and foresee it -- probably, thats my (a bit lazy) position. :P