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 Leap Wireless (Nasdaq: LEAP) rose more than 14% in early trading and remain up more than 12% as of this writing. Insiders and institutions have stepped up buying as the stock has fallen.

So what: Notable buyers include new board member Richard Roscitt and the MHR Fund, the latter which increased its stake to 25.9% of the shares outstanding, theflyonthewall.com reported.

Now what: The buys are interesting in that they come after a massive plunge in Leap's stock price. Yet the purchases could prove Foolish. Leap trades for 0.20 times sales. Thus, at current prices, the market value of $1 of Leap revenue is just $0.20. Count MHR and Roscitt among those who believe that valuation is unfair. Do you agree? Disagree? Weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. He didn't own shares in any of the companies mentioned in this article at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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