The generation of shear flow by drift waves is an important area of investigation. In a recent paper [Chen , Phys. Plasmas 7, 3129 (2000)] an elegant formalism was developed for the generation of shear/zonal flows by drift waves in a toroidal plasma. The study of shear flow generation in fluids and plasmas is put into perspective. In this paper it is shown how a simple slab geometry analysis can lead to a similar dispersion relation and highlight the subtle differences between the slab and toroidal geometries. (C) 2001 American Institute of Physics.