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: Wireless radio tower operator SBA Communications (Nasdaq: SBAC) is getting a bad signal today as its shares swooned by 10.4% on very heavy trading volume.

So what: You guessed it: SBC is another victim of the proposed merger between Deutsche Telekom subsidiary T-Mobile USA and all-American phone giant AT&T (NYSE: T). Fears that fewer competitors in the mobile space will lead to less infrastructure investment are hurting SBC, American Tower (NYSE: AMT), Crown Castle (NYSE: CCI), and other tower operators to various degrees.

Now what: If consummated, synergies in the T-Mobile deal will undoubtedly damage infrastructure companies and their stocks. But this colossus of a contract stands on feet of clay, much like the proposed but never completed attempt to combine Sprint (NYSE: S) and Worldcom eleven years ago. The final "yea" or "nay" from our regulatory systems will decide whether SBA is trading at a deep discount today or simply suffering as it should.

Interested in more info on SBA Communications? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. American Tower is a Motley Fool Rule Breakers selection. 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 is investors writing for investors.