My definition of exploitation comes from Marx:
Once Capitalists are able to pay the worker less than the value produced by the labor a surplus labor forms and this results in the capitalists' profit. This is what Marx meant by “surplus value,” which he saw as “an exact expression for the degree of exploitation of labor-power by capital, or of the laborer by the capitalist.”
http://en.wikipedia.org/wiki/Exploitation_of_labour
A pure entrepreneur doesn't get exploited because he gets all the profits. A full employee (working in a profitable enterprise) gets fully exploited because he gets the pay he agreed to when he was hired regardless of the profit he generates.
The sweet spot for the modern worker, in my mind, is to keep as much of the profit as is possible by being as close to the entrepreneurial end of the spectrum as possible.
The point is, there's more money to be made running a burger cart than working at McDonald's, cleaning houses from clients on Craigslist than working for Molly Maid, fixing cars yourself than working at PepBoys.
The main barriers to entry for these workers is marketing, book keeping, and inventory management, and all three of those barriers are reduced because of automation and globalization.