An online is simultaneously a , a competitor and a regulator.
It hosts sellers, sells its own goods beside them and writes the rules both must follow.
Each role is defensible alone, and holding all three creates a predictable conflict.
A platform sees which products sell before anybody else does.
It can then produce a similar item and place it above the original in the results.
Investigations in several countries found exactly this, despite public .
Remedies divide into and behavioural, and they differ in how much enforcement they need.
Separating the from the retail arm is and ends the conflict.
Requiring equal treatment is behavioural and requires somebody to check forever.
Regulators have chosen the second almost everywhere, because the first is politically enormous.
Fees are the quieter issue and matter more to a small seller than does.
, advertising, storage and returns together can exceed a third of the sale price.
A seller who refuses to advertise becomes invisible, which makes advertising a fee in practice.
rules that force a full fee schedule to be published are cheap and unusually effective.
A seller who can compare two platforms behaves differently from one who cannot.