Take a look at Brad D's blog--
www.j-bradford-delong.net/movable_type/index.html
for a criticism of the Marxist notion of exploitation. I know we shouldn't dogpile, but those of us who think that the extraction of surplus value is worth studying should offer a few comments on his blog. (Frankly, I don't think much of Brad's argument, but I'm interested in the opinions of LBOsters.)
Miles