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 Clearwire (Nasdaq: CLWR) have plunged today by as much as 20% after Verizon (NYSE: VZ) said it was selling some of its spectrum.

So what: Big Red is putting up some of its wireless spectrum in the 700 MHz frequency band as it hopes to gain regulatory approval to buy a different slice of spectrum from cable operators. Adding to the availability of wireless spectrum could reduce the value of other holders of spectrum like Clearwire and DISH Network (Nasdaq: DISH).

Now what: Both Clearwire and DISH are feeling selling pressure on the news, as their respective spectrum holdings comprise a sizable chunk of their value. At the end of last year, Clearwire valued its spectrum holdings at almost $4.3 billion -- nearly 49% of its total assets on the books. The company already has more than $4 billion in long-term debt. It's a real danger if the company's largest asset should take a hit.

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