The worst Excel user I've ever seen was my brother. At film school he was producing a student film. He did the budget in Excel. One day I came home from work an

The worst Excel user I've ever seen was my brother. At film school he was producing a student film. He did the budget in Excel. One day I came home from work and he had some questions waiting for me. Looking through his sheet, I noticed that his summation row at the bottom had hard-coded values rather than the =SUM(...) formulas I was expecting. Thinking he had inadvertently done a 'copy -> paste values', I said, "Look, you killed your formulas here." He asked, "What are formulas?". Turns out, he had been using a calculator to tally up all the columns and was typing the total into the cell at the bottom.