Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of CarMax (NYSE:KMX) were getting taken to the shop today, falling as much as 10% on a disappointing earnings report.

So what: Sales were actually strong for the used-car dealership chain as overall revenues increased 13%, to $2.94 billion, topping estimates of $2.87 billion, as same-store sales improved by a brisk 10%. Perhaps the strong sales growth is not such a surprise in a year that has seen domestic auto sales jump across the board. Despite the revenue gains, earnings per share missed estimates by $0.01, coming in at $0.47, as CarMax lost out in the lucrative auto-financing market. The market seemed to be especially disappointed that the jump in sales did lead to a stronger bottom-line performance.

Now what: The customers' shift to outside financing is certainly a curious development in this business, and will continue to threaten CarMax if it proves to be structural. CarMax also said third-party lenders were becoming stricter about handing out debt. As a result, the company is planning to test its own subprime lending originations, which could reverse the misfortune. With a well-known brand, and an auto market that's continuing to recover, CarMax does seem like it's poised for long-term success. I wouldn't count them out after one bad report.