<i>Most</i> social services fail.<p>There've been a slew of attempts. A handful, and I mean that literally, hit the big time at any moment: Facebook, Instagram, Pinterest, VK, Twitter, Reddit.<p>(That handful's composition may change, but its count largely doesn't. Zipf's Law may hold a clue as to why.)<p>Even massively financed efforts fail: Google+. I'm one of the ghosts in the ghost town, and measured the activity to boot.<p>Services who've studied other failures ... fail. Imzy.<p>Services who've gotten big ... fail. MySpace.<p>Services who sell for near a billion dollars ... fail. Bebo.<p>Even services that ... sort of succeed, fail to generate sustainable revenues. Twitter and Reddit.<p>There are many problems, and initially, they tend overwhelmingly to be <i>social</i> -- who is on the network. Several of the noteable successes hit big, in particular Usenet, Slashdot, and Facebook, at least in their day. Draw the <i>wrong</i> initial crowd, and you'll be hampered by it forever.<p>There's a whole slew of other challenges: spam, abuse, asshats, network and system attacks, costs, UI/UX, performance, relevance, utility, and more. Whilst there are technical components, many of the elements are dominated by soft-skills.<p>Commercial and centralised systems have tended to be the more successful, through technical simplicity and funding, though there are noncommercial successes: Wikipedia and the Wikimedia foundation, MetaFilter.<p>And some interesting efforts at a slow boil: GnuSocial, Diaspora, Mastodon.<p>I'm not convinced decentralisation is the core problem.