I'd say:
Commodity exchange and its corollary private property are the most
effective means of creating material scarcity as well as material
wealth. The project of a non-commodity society can rest only on the
possibility of keeping up the production of material wealth while
destroying the need for creation of material scarcity.
It is interesting to note that certain "modern" economists had
announced the failure of the P2P at its outset because its operation
does not comply with the elementary rules of "economic rationality",
founded on individual selfishness. They announced learnedly that
everyone would be ready to take, but that nobody would be ready to
give, to make the effort to put something at the disposal of the
others. Some recognized thereafter their error and the need to
"reconsider" the theory. At least, they recognize that there is
something new. The old but effective argument against the very idea
of a truly communist society - "human selfishness" - has been
shaken, not just on ethical grounds but in practice.
I agree wholeheartedly and think this practically and on a large scale
basis overcoming of bourgeoise logic can not be overestimated.
AFAICS a couple of file sharing systems require the user to publish
stuff - at least what s/he downloaded herself. In a way this is more
of an exchange that simple file sharing. Can someone give us an update
about the current practices? I think it is important to think about
this. I have some ideas on this but since I'm not practicing file
sharing I'd like to hear about the practice first.