re: which marxism? which definition of exploitation?

the recent discussion re: which marxism? was/is very interesting. in this
context i have a question re: definition of exploitation. in my studies of
unequal exchange i observed that apparently many marxists cannot and will
not consider "unequal exchange" as a form of exploitation. i understand that
"unequal exchange" is not covered under the honest-to-marxness concept of
exploitation (which is closely linked to wage labor/surplus value). on the
other hand, any leftist observer of international and world-system economic
relations cannot but see that "something of an exploitative nature" is going
on between rich countries and poor countries, center and periphery.
Emmanuel, Amin et al. called this "unequal exchange". Cakmak speaks of
"world technological rent". wouldn't it be time to subsume this under the
general concept of exploitation? this enlarged concept of exploitation would
have two (or more) subconcepts -- (a) narrow definition of exploitation a la
Marx; (b) "unequal exchange", "world technologcial rent" and similar, also
(c) no name -- e.g., when a Canadian company changes the status of a person
from employee to subcontractor it effectively increases the exploitedness of
that person, while liberating that person from being exploited in the
honest-to-marxness sense. (b) and (c) were no significant issues at Marx's
time, just like birth control pills were no issue at the time of Moses,
Jesus, Mohamed and other major thinkers. From a WS perspective, an enlarged
concept of exploitation appears called for. what do others think about that?

gernot kohler