LJ/DW/blogs are still best for deeper discussions or personal pondering-out-loud. Shorter status updates and news seem to have migrated elsewhere, and many of my LJ friends hardly post there anymore.
Facebook is spammy with viral apps and silly games and evil with their handling of personal information, and the interface scrapes (despite changing unexpectedly every couple of months), but some of my friends only seem to exist online there anymore. I can either hold my nose and scan it, or let go of those connections. And my mom's over there.
Twitter is too difficult to track anything more than 15 minutes old, and is swamped with retweets that drown out actual personal news, and is too constrained for anything besides open-loop.
G+ I had great hopes for, briefly, but given the 'nyms and account-names issues and corporate muscle-flexing, it has lost IMO whatever moral edge it had over Facebook. And I don't see many threaded discussions on G+, and relatively few friends actually have continued posting once the shiny wore off. It is feeling more Friendster-like...
And then there's Usenet, where I used to focus up until about a decade ago, on newsgroups. They still exist, but I don't know most of the handles anymore and there's no way to screen or any privacy.
Tracking *everything* takes too many cycles. So I'm increasingly tracking *nothing*, or only spot-checking my sweeties and closest friends when I have a few moments. I miss the online community sense that once seemed to exist... and I don't have any answers. Chaos and increased noise-to-signal seem to me to be increasing.