Just yesterday with a colleague.
Her to me: "Well how am I supposed to know that?! Nobody's ever told me that or showed me how to do it!."
Me to her: "I showed you that, about six weeks ago, you sat next to me and wrote the instructions down click-by-click of when and how to do it."
Her to me: "(leafing through notebook) If I had, I'd have the instructions how to do it and I've definitely not got any instructio ... oh."
Bought 3 cds in a charity shop today. Christina Aguilera - Stripped, The Very Best Of Sheryl Crow and Natalie Imbruglia - Left Of The Middle all for the grand price of 3 pounds. Win!