Offhand, I can't think of any sf which has explained why a return of a feudal system is plausible
In the Vorkosigan series, the main events surround a planet with a feudal system. This is explained because the planet lost contact with the larger galactic civilization and regressed in tech level massively. Meanwhile certain powerful bandits and raiders became strong enough in the chaos and passed down their roles on to their children. Then when they ended up being reconnected with the advanced technology societies they became very quickly a feudal culture with advanced technology. One major aspects of the stories is how this is an inherently unstable situation. (I have to wonder if this is in deliberate contrast to something like Dune where society stagnates in a feudal system with advanced tech for hundreds of years.)
I've seen several people on Less Wrong recommend Mencius Moldbug's writings, and I've been curious about how he became so popular here. He's certainly an interesting thinker, but he's rather obscure and doesn't have any obvious connection to Less Wrong, so I'm wondering where this overlap in readership came from.
[EDIT by E.Y.: The answer is that he's not popular here. The 2012 LW annual survey showed 2.5% (30 of 1195 responses) identified as 'reactionary' or 'Moldbuggian'. To the extent this is greater than population average, it seems sufficiently explained by Moldbug having commented on the early Overcoming Bias econblog before LW forked from it, bringing with some of his own pre-existing audience. I cannot remember running across anyone talking about Moldbug on LW, at all, besides this post, in the last year or so. Since this page has now risen to the first page of Google results for Mencius Moldbug due to LW's high pagerank, and on at least one occasion sloppy / agenda-promoting journalists such as Klint Finley have found it convenient to pretend to an alternate reality (where Moldbug is popular on LW and Hacker News due to speaking out for angry entitled Silicon Valley elites, or something), a correction in the post seems deserved. See also the Anti-Reactionary FAQ by Scott Alexander (aka Yvain, LW's second-highest-karma user). --EY]