Bidders estimate a common value with error; the highest bidder is usually the one whose error was largest and positive. So winning is bad news about your estimate.
The correction: shade your bid below your point estimate, by an amount that grows with the number of competitors - more bidders means the winner is a more extreme outlier.
The interview form: "ten firms bid for an oil field; your geologist says 100 million; what do you bid?" Considerably less than 100, and explaining why is the answer.
Same mechanism as adverse selection.