  We study the current-algebra approach to the Gerasimov-Drell-Hearn sum rule,
paying particular attention to the infinite-momentum limit. Employing the
order-alpha^2 Weinberg-Salam model of weak interactions as a testing ground, we
find that the legitimacy of the infinite-momentum limit is intimately connected
with the validity of the naive equal-times algebra of electric charge
densities. Our results considerably reduce the reliability of a recently
proposed modification of the Gerasimov-Drell-Hearn sum rule, originating from
an anomalous charge-density algebra.
