I love this technique. It's fun to use on missionaries - I got a couple Mormons a while ago and was able to chatter excitedly about how I'd got this tenet and that article down because of other correspondences, but now they were here, and I'd heard missionaries had special knowledge of these things, and maybe they could clear up one or two points of confusion? It turns out that the best way to get rid of missionaries is to be sincerely sorry to see them go.