The Stanford Encyclopedia of Philosophy has just published a very heavily revised version of my entry on “Exploitation.” In addition to covering relatively recent developments in the literature, the essay now contains an extended treatment of Marx’s theory of exploitation, and several-neo-Marxist accounts.
It also, BHL readers will be happy to know, contains some discussion of various classical liberal theories of exploitation. This includes a short presentation of John Locke’s view as set forth in his Venditio, in which Locke claims (as do many libertarians) that the just price is equivalent to the market price, but also claims (as do many critics of the libertarian view) that it is nevertheless possible for market actors to charge desperate customers an unjustly high price. It’s a a subtle and, I think, fairly compelling view. See Mike Munger here for a somewhat lengthier summary and discussion of it.
The entry also contains a discussion of the 19th century libertarian Thomas Hodgskin’s discussion of exploitation as presented in his essay, The Natural and Artificial Right of Property Contrasted. And a brief presentation of the views of the French Industrialists such as Charles Comte and Jean-Baptiste Say. What both of these views have in common is that they go beyond looking at the ways in which individuals can take unfair advantage of each other in the market place, and talk about how the state can be used as an instrument of exploitation. Highly relevant to today’s concerns about corporate welfare and crony capitalism! Here’s an excerpt:
Even before Marx, then, we see in the 19th century a tight connection between theories of exploitation and theories of class and of class conflict. Marx himself credited the “bourgeois economists” of the French Industrialist school with having pioneered the economic analysis of class struggle (Marx & Engels 1965: 69). For members of that school, the two great classes into which society was divided were productive laborers and unproductive social parasites. The class of productive laborers was understood broadly to encompass not only those who exerted physical labor to create tangible goods and services, but anyone who worked to make goods more useful than they would otherwise be—so laborers, yes, but also entrepreneurs, arbitrageurs, and even capitalists in their role as managers and overseers of investments. The unproductive classes, in contrast, consisted of those who consume value but do not produce it, such as the army, the government, and the state-supported clergy (Raico 1977: 395).
According to Industrialists such as Charles Comte and Jean-Baptiste Say, the unproductive classes are able to maintain themselves by using the coercive power of government to forcibly extract resources from the productive. Taxes and tariffs were the most obvious forms such “plunder” could take, but the same goal could also be achieved by special protections for favored industries including the limited conferral of monopoly power (Say 1964: 146–147).
You can read the whole thing here!
 The original entry was written by the late Alan Wertheimer, who brought me on board as a co-author a few years back. This entry involved an almost complete re-write by me, though there are still a few sections that Alan wrote himself. I owe a tremendous debt of gratitude to Alan for shaping my thinking on this topic. But it’s probably safe to say that any errors in the present draft are my responsibility alone.