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 coin-counter and Redbox DVD renter Coinstar (Nasdaq: CSTR) dropped as much as 27% today after the company updated its fourth-quarter earnings guidance.

So what: Live by the Redbox and die by the Redbox. Or at least that's what Coinstar's latest projections seem to show. The company cut its projected earnings range to $0.65 to $0.69 per share from previous guidance of $0.79 to $0.85. Analysts, on average, were looking for $0.84. The company placed much of the blame on the 28-day delay on new titles that the company had agreed to. Interestingly, my fellow Fool Anders Bylund noted that while Netflix (Nasdaq: NFLX) agreed to the same delay, it has actually been a plus for Netflix.

Now what: It's hard not to think that investors are overreacting here. Stepping back to look at the bigger picture, Coinstar noted that at Redbox -- 28-day problems and all -- revenue grew 38% year over year and same-store sales grew 12.5%. Analysts are likely to chop their 2011 earnings forecasts after this fourth-quarter disappointment, but if investor pessimism continues, Coinstar's shares start to look interesting -- even for non-growth-investors like me.

Want to keep up to date on Coinstar? Add it to your watchlist.           

Netflix is a Motley Fool Stock Advisor pick. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.                                                                      

Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his Motley Fool CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.