I use(d) Twitter as more of a meta-aggregator. It had actual social interactions combined with the sort of pointers out to news sites, tech blogs, etc. Perhaps I'm an outlier in how I use(d) it but I haven't come across anything that provided the same degree of convergence. This is precisely because it's mixing in short snippets from friends, acquaintances, and other people I find interesting.

> Instead, limit content on social sites to the subject of the platform

That's my point. I'm saying the thing I liked most about Twitter was that there wasn't a single "subject of the platform". Don't get me wrong, I also spend plenty of time in more specific corners of the internet, but I've yet to find something that quite replicates Twitter for me.