It reminds me of a critique of threads in The Art of Unix Programming (available at http://www.catb.org/esr/writings/taoup/html/ch07s03.html#id2...). And now that I look it up, it actually cites the Ousterhout paper! This suspicion of threading was one of the few parts of that book I found unconvincing, personally, but it's another witness that they have worried some people for a long time.