If I'm right, the effect of widespread propagation of such memes will be to snuff out what chance of survival and success humanity might have had. Unlike UFAI which is pure science fiction, the strangling of progress is something that occurs - has occurred before - in real life.
What would you consider to be the minimum estimate of the probability that I'm right, necessary to "reasonably" motivate concern or action?
I'm not quite sure what "you being right" means here. Your thesis is that propagating the UFAI meme will suppress scientific and technological progress such as to contribute non-negligibly to our destruction?
I'm afraid I don't have much background on how that's supposed to work. If you can explain what you mean or point me to an existing explanation, I'll try and give you an answer, rather than reactively throwing your question back at you.
In the early 1980s Douglas Lenat wrote EURISKO, a program Eliezer called "[maybe] the most sophisticated self-improving AI ever built". The program reportedly had some high-profile successes in various domains, like becoming world champion at a certain wargame or designing good integrated circuits.
Despite requests Lenat never released the source code. You can download an introductory paper: "Why AM and EURISKO appear to work" [PDF]. Honestly, reading it leaves a programmer still mystified about the internal workings of the AI: for example, what does the main loop look like? Researchers supposedly answered such questions in a more detailed publication, "EURISKO: A program that learns new heuristics and domain concepts." Artificial Intelligence (21): pp. 61-98. I couldn't find that paper available for download anywhere, and being in Russia I found it quite tricky to get a paper version. Maybe you Americans will have better luck with your local library? And to the best of my knowledge no one ever succeeded in (or even seriously tried) confirming Lenat's EURISKO results.
Today in 2009 this state of affairs looks laughable. A 30-year-old pivotal breakthrough in a large and important field... that never even got reproduced. What if it was a gigantic case of Clever Hans? How do you know? You're supposed to be a scientist, little one.
So my proposal to the LessWrong community: let's reimplement EURISKO!
We have some competent programmers here, don't we? We have open source tools and languages that weren't around in 1980. We can build an open source implementation available for all to play. In my book this counts as solid progress in the AI field.
Hell, I'd do it on my own if I had the goddamn paper.
Update: RichardKennaway has put Lenat's detailed papers up online, see the comments.