  In General Gauge Mediation (GGM), supersymmetry breaking is communicated to
the Standard Model (MSSM) sector via gauge interactions at a high scale which
we refer to as the messenger scale. At this scale GGM predicts certain sum
rules between the MSSM sfermion masses. We investigate the validity and the
ultimate fate of these sum rules after RG evolution down to the electroweak
scale where the mass spectrum will be probed at colliders. We find that the sum
rules hold for the first two generations. However the third generation (where
sfermions are lightest) violates one of the two sum rules by 10 to 50% over the
explored parameter space. This constrains and quantifies the potential use of
sum rules as a signature of gauge mediation. We also comment on the role played
by the messenger scale in single- and multi-scale GGM models.
