As pointed out earlier, it is not at all surprising that Cashill is able to find some passages in the Obama and Ayers books that have some superficially impressive similarities (he says that he "could identify twenty parallel passages just as compelling": this looks like pure bluster, until he has done so explicitly). But such superficial similarities totally fail to address the point made above about the contrast in the two writers' talk of memory. In 13 passages out of 15, Ayers talks of what memory is (or does) in the abstract. If he was also the author of Obama's book, then one would expect to find some reasonable proportion of similar passages within it, whereas one does not find any at all. The fact that one passage in Dreams which mentions memory is somewhat similar to a passage in Fugitive Days which does not mention memory is entirely irrelevant to answering this point. Cashill, apparently, ignores this simple logic, and so rashly bets his house against my mailbox on the matter. I hereby accept the bet. Let him put up, or shut up. If he is indeed prepared to bet his house on the outcome, then it may well be worth my investing more time on the issue to set out to prove at length that he is mistaken, rather than merely arguing (as I have done so far) that his case as presented is hopelessly unproven.
To sum up, I have found no evidence for Cashill's ghostwriting hypothesis, and rather strong (albeit limited) evidence against. Note, moreover, that the discussion above is all fought on his own chosen ground - analyses and literary patterns that he himself has cited as likely to tell in his favour. It is impossible to know without searching carefully what other evidence against his hypothesis might turn up if one were to look for it. But at least we must judge it as extremely unlikely, and indeed so far unsubstantiated. Moreover given its small initial probability (as a story that was always intrinsically unlikely - it would be very surprising if true), and the evidence already seen, I cannot imagine how the hypothesis could be rendered credible by further examination of the texts. Of course that doesn't mean it's impossible (for example if systematic comparative studies using Yavelow's system were to yield genuinely exceptional results), but I don't currently believe that anything short of documentary proof of Ayers's involvement will take the case further.