Brad De Long has, in response to an email, written a what he thinks is a little take-down of a marxist notion of exploitation. Basically, his argument is that when capital investment, the resources for which are provided by hard work and scrimping and saving, increases the resources for all, albeit differentially, so that workers, while not as well-off in resource terms as the capitalists, are better off than they were before the capitalists existed, no exploitation exists because a) the workers are better off and b) the capitalists worked to get what the advantages they have. I don't think this is very convincing, because the question asked by inquiring whether the workers are exploited is not whether they are better off than they otherwise would be, but whether they are getting their full entitlements. Since Marx assumes that we are entitled to the products of our labour, a claim De Long makes no effort to attack, the workers are exploited: even though they are better off, because they are not recieving the full product of their labour, they are being exploited by the capitalist, who is creaming part of it off.
Now, I don't find the claim that we are entitled to all the products of our labour very convincing at all, because it implies that anyone who does not work is exploiting those who do, including the elderly, children, the disabled and the sick, as well as making it justifying the existence of vast income differentials because of the differentials in market value of products (I know that Marxian economics posits the labour theory of value as the true value of goods, but that is simply implausible: are two identical chairs of different value simply because one took twice as long to make?). What is objectionable about the market is that it does not take into account the basic moral requirements imposed on our treatment of our fellow human beings simply in virtue of being fellow human beings, but rather hovers around an equilibrium where no further trades are advantageous, which may leave some incredibly wealthy and others in miserable poverty. We need to think rather about whether the distribution of costs and benefits as it stands justifiable to all those upon whom those costs and benefits fall. This seems to be something like what Matt Yglesias, despite his (hack, spit!) utilitarian tendencies, is saying.