I certainly think that "mediation" is an appropriate topic for discussion. I think that any time a collector collects, some amount of mediation takes place - that collector is the one who "mediates." It always exists when collecting takes place, but the matter to be discussed is the level of mediation, and the effect that the mediation has.
Certainly a valid topic for discussion.
Jack Campin's definition of mediation above is a pretty good place to start.

-Joe-