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 Motricity (Nasdaq: MOTR) dialed down in a big way today, shedding as much as 17% on huge volume.

So what: When a company goes public, insiders have to agree to not trade in the stock for a certain period of time. This "lock-up" is put in place so that shareholders buying into the IPO don't have to worry about insiders dumping their shares en masse once the deal closes. In the case of Motricity, there has been growing anxiety about the expiration of the lock-up, and the stock has now crossed the magical 180 threshold and insiders are now free to start selling.

Now what: Just because insiders can sell doesn't mean that they're going to. And if today's drop is being driven by concerns over insider selling, then it's a highly speculative move, and likely an overreaction. However, what I think is a more meaty concern is what's informing insider-selling anxiety -- that is, the stock's furious run since its IPO and its current lofty valuation. Will insiders sell in order to take advantage of the high valuation? Maybe, maybe not. But investors who are worried about that should take their own cue, pocket the gains, and find greener (and cheaper) pastures.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy assures you no Wookiees were harmed in the making of this article.