In reply to Jeremy Cherfas.

I'm in the same boat with you Jeremy. Each silo certainly has it's own set of functions, personality, and even audience. For me, Facebook and Instagram are more close friends and family, LinkedIn work-related, Twitter and Google+ generic town squares for interacting with people I might not otherwise meet in real life, and Foursquare/Swarm/Nextdoor are for interacting (albeit, not much) with neighbors and people in my geographic vicinity.
Twitter is almost too short in some sense while platforms like Mastodon, pnut, and 10C give more length and often feel more like chat rooms (or IRC or old multi-person instant messenger) interspersed with Twitter-like status updates. There's also a difference in who you're communicating with and which of your audiences they fall into (friends, family, real life acquaintances, internet friends, people with similar interests, etc.). Some of it comes down to interface, space given, and the organic nature of how the people in those communities choose to use them. Though Mastodon is very similar to Twitter, it's the more conversational direction that the users and community who are actively using it push it into that will determine some of its fate--certainly an interesting topic of study for cultural anthropologists.
Another thing I find interesting is their relative sizes. The smaller they seem to be (or perhaps closer to the Dunbar number of users they have) the more conversational and less "post-y" they feel. While I might syndicate some articles or status updates to some of these more chat-like services, I don't feel as much like syndicating all of my chat to them--at least until I could make my personal UI easier to use to do that, and that portends to be quite a way off.
As I bring up Dunbar's research, I also realize there are only so many slivers of the web that I can mentally keep up with at any given time. The closer I come to posting on my own site and interacting that way, the lower my cognitive load seems to become. I no longer spend time in or visit some of the major silos 3-10 times a day anymore since those interactions come back to me in a more natural way.