I’d agree with all of that bright, ample history to support your final conclusion. I would add that consideration is also needed between mountain bikers with different interests. I like jumps and berms, I also like natural trails and some need to be left that way.
copa – I share your concerns.
I suspect the increase in the numbers of people riding, and what they like to ride, is a key driver here. My initial reaction to theraq’a “huge groups” was “what?” – but you are right, formal (almost club-like) groups are springing up all over and they do tend to form quite visible groups at weekends. I guess some people will be offended by the mere presence of large numbers of cyclists, not sure what can be done about that. If there is only two or three of you, you can say hello, exchange pleasantries about dogs/horses/the weather and generally chat people up. That’s not so practical in a large group.