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 prepaid wireless carrier Leap Wireless (Nasdaq: LEAP) are getting disconnected today, down by as much as 10% after the company was downgraded by Jefferies.

So what: Jefferies cut the stock's rating from buy to hold, while also lowering its price target from $12 to $10. The sell-off is a knee-jerk reaction to the negativity, despite the fact that even a $10 price target is higher than yesterday's close of $9.25, and much higher than the low of $8.31 seen so far today.

Now what: Leap markets its prepaid services under the Cricket brand, and Jefferies cites added risks on the horizon as larger carriers start to focus more on the prepaid segment. In related news, Jefferies upgraded Verizon (NYSE: VZ) from hold to buy while also boosting its price target on that stock from $33 to $45. Fellow prepaid carrier MetroPCS (NYSE: PCS) also felt some wrath as Jefferies knocked its price target from $15 to $12, although it was able to keep its buy rating.

Interested in more info on Leap Wireless? Add it to your watchlist by clicking here.

Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. 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. The Motley Fool has a disclosure policy.