Arstechnica posted a reminder about complacency, privacy issues and validating data. While the article focuses on industrial and corporate environments, there is some takeaway for home use as well.
The eye-catching line:
Industry studies show that 90 percent of spreadsheets containing more than 150 rows have at least one major mistake.
The risk of error obviously increases the more hands are in the spreadsheet cookie-jar, so to speak. However, I have found a lot of common errors from things like fonts. Banks often use small, challenging fonts on statements that can easily make either a 6 or an 8 look like the other, for example. I also have a habit of verifying the SUM calculation for anything important by copying the raw text to BBEdit, or something to strip any formatting, and then dropping it into another spreadsheet app to re-run the total.
[Edit: Fixed a silly typo in 3rd sentence that did not alter original content.]