Propagation effects are well known to limit the sensitivity of pulsar searches based on periodicity detections. I define several regimes for pulsar searches that are based on whether the search sensitivity is luminosity limited, dispersion limited or scattering limited. Consideration of these regimes allows general statements to be made about pulsar searches in and out of the Galactic plane. Telescope size matters, but only to a point. Once scattering becomes important it is better to search more sky (in a blind survey) than to integrate longer on a given sky position. Example surveys are described.