Brooks Taylor's recent mistake involved building revenue tables in his company's self-service and invoice side of the business, where he tried to update old historical records with a simple timestamp change to facilitate analysis. However, this seemingly harmless action triggered a series of underlying calculations that relied on the same data, ultimately resulting in a loss of $5 million. The incident highlighted the interconnected nature of modern data ecosystems, emphasizing the importance of considering potential downstream effects when making changes, even if they appear minor. This experience serves as a cautionary tale for data professionals, illustrating the need for careful consideration and attention to detail in their work.