Once again, in English, please.   ;D 

Do you mean that there's been some bad blood?  I know in one forum I belong to, some of the members very enthusiastically advertised a new Facebook group for the same modeling genre, encouraging everyone to join, and then several of them cut back their activity in the forum, focusing on the FB group.  They were veterans of the forum, charter members, if you will, and I think there was a feeling that they were abandoning the forum, and giving a bit of an insult to the forum's founder and all the work he did.  However, I don't think there was an open break between the two groups, and he eventually began to post some things on FB as well.  But some of us decided to make sure we continued to use the forum, out of respect and attachment to its founder.

Facebook hasn't changed my forum activity that much; I do post some build blog info there, but more, I post finished things there.  Facebook is really more for my family and friends to have a look at what I do.  No, what changes my forum activity is when a new forum comes out, and someone tells me I need to join.  Then I realize that I just don't have time to be an active member of so many forums, and I keep to my core group of forums.