One week, someone came back for their second time and was most miffed that I couldn't remember his name from the previous week. So miffed in fact that they declined - no, 'refused' would be a better word - to remind me, and continued to do so ever afterwards. I soon stopped bothering to ask.
Today, I saw them again, with someone rather more sensible and now I know.
Not that I'm likely to remember, mind.