I have a 600 word pro-futarchy oped in the current issue of BBC Focus magazine. It begins:
Has the recent MP expenses scandal soured the idea of democracy for you? Good, because a vast space of possible forms of government remains unexplored, and it is high time we explored it. Yes, democracy beats a dictatorship, but there might be better systems. …
Mike you are imagining an extreme worst case, not a typical case, and yes it just has to be better than what we have now. The mechanism I'm suggesting doesn't infer things from time changes, so it doesn't have the interaction problem you imagine.
Another problem is disentangling the effects of competing policies.
For instance, perhaps I propose (and the speculation market agrees) that some form of regulation of some industry will increase some social welfare statistic. But at the same time someone else proposes (and the speculation market agrees) that some form of industry taxation will increase some social welfare statistic. If the statistic goes down, it might be very difficult to tell which policy was wrong, or if both were wrong. It could also be that the statistic goes up, even though one policy was wrong, because the benefits of the other were so great.