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 Star Scientific (Nasdaq: CIGX) fell more than 13% in early trading before closing down 3.5%. The Big Move was the stock's third since the beginning of June, twice to the downside.

So what: In many ways, the cigarette maker is a trader's dream. High-beta stocks such as Star Scientific -- which tends to move twice as much as the overall market -- offer plenty of opportunity to get in and out in a given day, eking out gains along the way.

Now what: Yet there’s a good reason we Fools advise caution when it comes to trading in Mr. Market's Mega Movers. One day of bad timing could cause years of portfolio grief. Bear that in mind before you "play" Star Scientific at these levels. Do you agree? Disagree? Weigh in using the comments box below.

Interested in more info on Star Scientific? Add it to your watchlist .

Fool contributorTim Beyers is a member of theMotley 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'sportfolio holdings andFoolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insightsdelivered directly to your RSS reader.

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