PACS Codes: 41.75.Ht, 41.75.Fr, 29.25.Bx Projected next-generation linac-based light sources such as PERL 1 or the TESLA free-electron laser (FEL) 2 generally assume, as essential components of their injector complexes, long-pulse photocathode rf electron guns. These guns, due to the nature in which they are operated, may be more susceptible to ion bombardment damage of their cathodes than conventional rf guns. This paper explores this possibility and presents a basis for future study of the subject.