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 Latin American wireless carrier NII Holdings (Nasdaq: NIHD) plunged today, down by as much as 11% after the company reported earnings this morning.

So what: Revenue in the fourth quarter tallied up to $1.6 billion, a bit short of the market's expectation of $1.68 billion. However, the real shocker was the bottom line, and the loss of $0.05 per share was a big surprise compared to the $0.19-per-share profit that the Street was looking for.

Now what: The company added 467,000 net subscribers during the fourth quarter, but attributed the surprise loss to an unexpected rise in costs related to network deployment and marketing. Increasing competition led to higher spending to build its brand and retain customers. Forward-looking guidance also came in a tad light, with fiscal 2012's revenue forecast of $7.1 billion falling short of the $7.3 billion consensus.

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