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 wireless services provider MetroPCS (NYSE: PCS) were getting no bars from investors today as shares fell as much as 11% in reaction to the company's third-quarter earnings.

So what: On the bright side, revenue for the third quarter was up 18% from last year and basically in line with analysts' estimates. Total subscribers at the end of the quarter were 9.1 million, up 16% from 7.9 million at the end of last year's third quarter.

However, customer churn rose, net subscriber additions slowed, and profitability suffered. Adjusted EBITDA as a percentage of service revenue -- a measure of profitability -- fell to 28.9% during the quarter, from 33.4% last year. Meanwhile, net income dropped 10% and earnings per share clocked in at $0.19, down from $0.22 last year and short of the $0.23 that analysts were looking for.

Now what: I can't say that this is the kind of business that appeals to me at all. The business itself is highly capital intensive and with massive competitors like AT&T (NYSE: T) and Verizon (NYSE: VZ), every inch is hard-fought. Certainly this doesn't mean that MetroPCS can't be successful, but investors will want to watch the coming quarters closely to see whether higher churn and slower growth become a trend.

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