  In its continuous version, the entropy functional measuring the information
content of a given probability density may be plagued by a "measure" problem
that results from improper weighting of phase space. This issue is addressed
considering a generic collision process whereby a large number of
particles/agents randomly and repeatedly interact in pairs, with prescribed
conservation law(s). We find a sufficient condition under which the stationary
single particle distribution function maximizes an entropy-like functional,
that is free of the measure problem. This condition amounts to a factorization
property of the Jacobian associated to the binary collision law, from which the
proper weighting of phase space directly follows.
