One somewhat spreadsheet-related error I experienced firsthand was when most people in the class I was in got the wrong grade for the final. The professor had o

One somewhat spreadsheet-related error I experienced firsthand was when most people in the class I was in got the wrong grade for the final. The professor had ordered the students alphabetically in a spreadsheet, then copied their grades from there to the website. But one student had a name with a non-ascii character, and the spreadsheet and the website disagreed on on the alphabetical ordering in that case, so most students got the grade of the person alphabetically next to them.