Two basic reasons here: the restructuring of everything around commerce (ads, shopping carts), and a much broader technological imperative that views everything as a resource to be optimized, thereby reducing everything to its data.
This reduction is not merely a way of thinking – it also acts, or legislates – witness how Facebook has restructured the very idea of friendship around likes and recommendations. Not simply the idea of relationship but the relationships themselves have been transformed.
So if anything worthwhile is to exist it will always be in the margins, in making use of discarded technologies, or byproducts or inefficiencies that arise along the way. The fact that something like LiveJournal came to exist at all was accidental – someone was experimenting, trying to learn web technologies and the community just kind of built itself.
But the margins don’t endure – it’s like building a house on quicksand. The only certainty is the absolute precarity of the margins and of marginal existence. So this basic process of even trying to exist online – or trying to exist at all, for that matter – is always one in which one is forced to move between platforms, use technologies which have been abandoned, or where things don’t work. People – usually the ones with the most to offer – get discouraged and stop. And there is no guarantee that new people will fill the void.
I see all this in the fact the few blogs that I follow really aren’t “social” at all – comments are minimal or nonexistent, it mostly just goes back to one individual’s long-form writing (or sharing of other media), and occasionally some links to other blogs (most of which are broken).
e.g.
http://50watts.com
https://blogthehum.com [no longer updated]
http://www.johncoulthart.com/feuilleton/
https://itself.blog
etc.
I do follow a few tumblrs but find the process quite discouraging – mostly reblogs leading
back to other reblogs, never quite getting to the source of anything, way too much noise. There’s also something very twitter-like in the format which seems to discourage substantive contributions. So – always with great effort, but sometimes a few gems can be found.
Anyway – for the most part I’m resigned to all of this stuff, my own activity especially – being marginal, forgotten, not archived, not remembered, it’s the very way it’s constituted that makes it unsustainable.