In the day job, I point out that the "Mr Market" metaphor can be be misleading. If markets are complex emergent processes, as Alan Kirman shows, prices and quantities cannot be seen as the result simply of an individual's behaviour writ large, and markets are unpredictable.
Such a conception is consistent with Marxian concepts of alienation and reification. In capitalism, said Marx, "the productive forces appear as a world for themselves, quite independent of and divorced from the individuals." Or as Lukacs put it:
A relation between people takes on the character of a thing and thus acquires a ‘phantom objectivity’, an autonomy that seems so strictly rational and all-embracing as to conceal every trace of its fundamental nature: the relation between people.
Insofaras there is a justification within Marx's writings for a centrally planned economy - and, right-wingers please note, Marx wrote very little about central planning - it probably lies here. Central planning is, allegedly, a means of bringing an alien process under conscious human control. In this sense, modern work on complexity helps to buttress classical Marxism.
This poses the question: should we care about alienation in this sense? I don't think we should.
For one thing, as John Roemer says (pdf), for many people, alienated work can be a liberating force. (There's an analogy with urbanism here: many people welcome the freedom that anonymous city living gives them).
And for another, it's not obvious that central planning actually can bring market forces under human control, at least not without huge cost in terms of foregone innovation.
Instead, I suspect that the sense in which alienation mattered most to Marx - and should matter to us - is a slightly different one. It's that, in producing capital and profits, workers saw the products of their labour become means of their domination:
The object which labor produces – labor’s product – confronts it as something alien, as a power independent of the producer. The product of labor is labor which has been embodied in an object, which has become material: it is the objectification of labor...Under these economic conditions this realization of labor appears as loss of realization for the workers; objectification as loss of the object and bondage to it.
The problem here, though, is not so much alienation as domination, in the sense of oppressive working conditions, and inequality. These problems, we now know, are not necessarily solved by central planning, but are perhaps soluble by more equitable market processes.
I say all this for two reasons. First, to ask the left: what exactly is wrong with capitalism, and do those problems really need central planning to fix them? Secondly, to point out to the right both that Marx's conception of the economy is consistent with new thinking about complexity, and that one of his concerns was to expand freedom, in the sense of better enabling people to take charge of their destiny. Yes, central planning failed to achieve this, but I don't think this discredits the Marxian project.