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 China MediaExpress Holdings (Nasdaq: CCME) plunged more than 12% in early trading and remain down more than 9%, continuing a tenacious tussle between long and short investors.

So what: Traders must love this stock. In the past month alone, shares of China MediaExpress have traded between $10.66 and $17.15 each. Roller coasters have nothing on the stock.

Now what: Such stomach-churning volatility has to make investors nervous. And yet there is a growth story here. China MediaExpress claims the leading position in providing bus-based TV ads to China's up-and-coming consumer class.

Citron Research says management's faking. Wall Street analysts say otherwise, projecting 22.5% annualized profit growth over the next five years, resulting in a nearly microscopic 0.24 PEG ratio. Who do you believe?

Interested in more info on China MediaExpress Holdings? Add it to your watchlist. You can also try any of our Foolish newsletter services free for 30 days.

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 Twitter as @milehighfool. You can also get his insights delivered directly to your RSS reader. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is also on Twitter as @TheMotleyFool. Its disclosure policy is at least 10% better than other disclosure policies.