Are 'Social Networks' Dumbing Down Internet Discourse?

Are 'Social Networks' reducing web traffic and demand for 
UseNet and Moderated Subject Groups?

As entities like Facebook, SnapChat, and Twitter gain
users, I've noticed two disappointing trends on both 
UseNet groups and specific topic oriented moderated 
groups:

1) Especially on Usenet - the amount of non-topic-
related chatter - 'smut' for lack of better term.

2) On both Usenet and in moderated subject groups:
a steepening decline in new threads, and, less frequent 
response to new questions and existing threads.  

I feel  that  dedicated subject newsgroups  and moderated 
subject  groups  exist  for  a good  reason, and fill a 
role  that  no  shallow  social  network  could  ever hope 
to  replace.