Nanotech x-risk would seem to come out of mass-producing weapons that kill survivors of an all out war (which leaves neither side standing), like systems that could replicate in the wild and destroy the niche of primitive humans, really numerous robotic weapons that would hunt down survivors over time, and such like.
What about takeover by an undesirable singleton? Also, if nanotechnology enables AI or uploads, that's an AI risk, but it might still involve unique considerations we don't usually think to talk about. The opportunities to reduce risk here have to be very small to justify LessWrong's ignoring the topic almost entirely, as it seems to me that it has. The site may well have low-hanging conceptual insights to offer that haven't been covered by CRN or Foresight.
to justify LessWrong's ignoring the topic
That's a much lower standard than "should Luke make this a focus when trading breadth vs speed in making his document". If people get enthused about that, they're welcome to. I've probably put 50-300 hours (depending on how inclusive a criterion I use for relevant hours) into the topic, and saw diminishing returns. If I overlap with Eric Drexler or such folk at a venue I would inquire, and I would read a novel contribution, but I'm not going to be putting much into it given my alternatives soon.
Why does SI/LW focus so much on AI-FOOM disaster, with apparently much less concern for things like
Why, for example, is lukeprog's strategy sequence titled "AI Risk and Opportunity", instead of "The Singularity, Risks and Opportunities"? Doesn't it seem strange to assume that both the risks and opportunities must be AI related, before the analysis even begins? Given our current state of knowledge, I don't see how we can make such conclusions with any confidence even after a thorough analysis.
SI/LW sometimes gives the impression of being a doomsday cult, and it would help if we didn't concentrate so much on a particular doomsday scenario. (Are there any doomsday cults that say "doom is probably coming, we're not sure how but here are some likely possibilities"?)