Quarterly earnings calls have become the weather vanes of the uncertain economy, each one drawing interest as a gauge of spending trends in telecom.

But although there's consistency in the tone of telecom service providers — general acknowledgement of "challenging" times, etc. — the economy isn't affecting all of the market's players in the same way. These are the times that separate losers from those who aren't losing as much.

Service providers should expect to see more volatility among small business customers — many of those customers will go under, and new ones won't be so quick to replace them. And they may see purchase delays among larger customers. Those trends are evident in second-quarter earnings, as providers on the lower end of the market are feeling more pressure than those at the higher end. Level 3 declared strong market demand and positive free cash flow but relatively flat revenue. Meanwhile, Paetec and Cogent Communications both lowered their revenue expectations for this year. And the message from CBeyond, which focuses largely on small businesses in particular, was essentially: Hey, at least it's not getting worse.

The good news is that there is still opportunity for any CLEC to grow, even in this sour market. When business is booming, competitors can comfortably watch the tide lift every boat. But a harsh economy presents an opportunity for every carrier to take market share.

"CLECs that are taking share can still do well in a flat market," financial analyst Donna Jaegers told me in this recent interview, pointing out that Bell companies still own three-fourths of most local markets, leaving plenty of room for rivals.

TWTelecom CEO Larissa Herda acknowledged as much in the company's earnings call yesterday, saying, "Let's face it, we have low market share, which allows us to take share and grow, even [in a slow economy]."

A silver lining that, for some companies, could be turned into gold.