At some point, a couple of months ago, I noticed that my Facebook feed devolved into 9GAG reposts and random things about people I sometimes knew, often not. Twitter wasn't any better — it was mostly flame wars about web development issue du jour.
This wasn't the case of me just not grooming the feeds. I heavily curated Twitter accounts I followed, and my Facebook friends are my actual real-life friends (or at least real-life acquaintancies I'm on a friendly basis with).
The trouble was — I still spent a lot of time on both Twitter and Facebook! It's easy to get drawn into a Twitter conversation, or follow trails of meme images. And before you know it, half an hour has passed. While sometimes something genuinely interesting came up, signal to noise ratio was too low.
So I decided to just visit occasionaly, a few times a week. I'd go over interesting stuff, ignore the pointless drivel, still get some value out of the experience, have fun and not waste too much time.
But coming back to Twitter and Facebook after a few days felt like watching a soap opera after a few days' pause. Nothing much happened in the meantime — certainly nothing digging for in the unwidely Twitter and Facebook user interfaces. Having stepped out of the stream, I found it even less appealling. It was boring and I stopped coming back.
In the above description, there's very little “social”. While Twitter and Facebook are social in the sense that people communicate over them, in most cases the communication is so shallow and ephemeral that it becomes meaningless. It's an endless, constant chit-chat.
It's Junk Social. Like junk food, it satisfies the immediate need, in this case for social contact, but its nutritional value for the psyche is low. And like junk food, it's easy to overindulge.
I unapologetically eat junk food — in small amounts. And I do think Junk Social can have value (and be fun) — in small amounts.
 Like Postmodern Jukebox
 While they put a lot of effort into the experience of the user consuming Now, it's obvious the use case of someone digging through Past is not high on the priority list.
 Notable exception is coordinating something in real-life, like setting up a meetup, pinging friends to go to the movies, organizing a charity drive or staging a revolution. The value here is always tied to the real-world behaviour, though, and using the social network as a communication tool, which is not exactly new — email, IRC, forums have all been used for this for decades.
 Twitter practically enforces this with their 140-character limit. It's impossible to have a thought-out, insigthful conversation there.
 Standard disclaimer applies: this is only my opinion, and I'm neither a nutricionist nor psychologist.