Language learning software maker Rosetta Stone (NYSE:RST) bought a little Seattle company called Livemocha on Tuesday. At just $8.5 million in value, this isn't the biggest acquisition in history -- but it may be the most important for Rosetta Stone.

In the following video, Fool contributor Rich Smith explains how Rosetta's quick purchase of Livemocha protects its business from threats like Google's (NASDAQ:GOOGL) YouTube, and challenges rivals including McGraw-Hill (NYSE:SPGI) and even Disney (NYSE:DIS) to up their game.

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