And when I hear about the envisioned ideals of a lot of AnCaps within the bitcoin community, what I hear is exactly what Marx described as the 'capitalist phase'. Although a lot of AnCaps don't seem to realise this, of course...
So, in a pure capitalist society, who would be exploited, and how?
People with access to capital would exploit those in need of it; until an equilibrium had been reached (this equilibrium could be in the form of unions, or mechanisation and the resulting balance would be one between cost of production and consumption of production.)
At some point the relationship would change from parasitic to co dependant (same as biological evolution), this is the shift Marx predicted would happen in the most industrialise and civilised states.
Ironically now we are being exploited through the likes of the capital behind the central banks, not the entrepreneurs or the typical capitalist Marx envisioned.
Marx thought through the free market a little further than Adam Smith, where Adam Smith saw the result of land lords exploiting there tenants as the mechanism to fuel homesteaders he stopped. I suspect he never questions humanity developing the whole world (or the possibility of continued exponential growth of the humans.) Marx on the other hand saw a point where access to land was one mechanism where the capitalists could keep the parasitic relationship between capital and labour alive.
Ironically Marx advocated the Central Bank model now being used to perpetuate the parasitic imbalance he sorts to expose and overcome.