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 optical components manufacturer Fabrinet (NYSE: FN) look blurry today, fading as far as 20.7% on very heavy volume.

So what: Analyst firms Stifel Nicolaus and Morgan Stanley just downgraded Fabrinet from buy to hold. We don't have any detail on the reasons for these harmonized hits, but Fabrinet recently said that floods in Thailand are having a material impact on operations in that crucial manufacturing space; the downgrades are likely reactions to the bad news.

Now what: Just when you thought no company could suffer as much from the Thai disaster as hard drive maker Western Digital (NYSE: WDC), Fabrinet comes along with a bigger hit. I saw a buy-in opportunity in Fabrinet three months ago, but shares have fallen 41% more from the prices I saw then. This time, there's severe damage to the company's operations, to the point where large customer II-VI (Nasdaq: IIVI) points to Fabrinet's flooding as a limit on next quarter's results. Let's just watch this company for signs of recovery and rebuilding before taking any action.

Fool contributor Anders Bylund holds no position in any of the companies mentioned. The Motley Fool owns shares of Western Digital and II-VI. Motley Fool newsletter services have recommended buying shares of II-VI. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinion, but we all believe that considering a diverse range of insights makes us better investors. Check out Anders' holdings and bio, or follow him on Twitter and Google+. We have a disclosure policy.