The main thing I want from that sort of social media is to see original content from people that I know. I don't want to see the best cat video; I want to see my friend's cat video.
There are already plenty products aimed at the mass populace, I would love to see again more communities built for the niches. Not just in terms of topics (subreddits et al), but functionality and interactions. Because honestly I came to the conclusion that communities only work if they stay relatively small and focused. I haven't used Are.na enough to say anything about their community specifically, but their approach resonates strongly with me.
Sounds like a key feature.
I think we've learned by now that mass adoption is the death signal for any platform since it will bring in the spammers, advertisers and other undesirables which ruin the experience.
I have a feeling that is going to alienate mass populace users.