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: Second verse, same as the first. As the trading week winds down to a close, Redbox provider Coinstar (Nasdaq: CSTR) is running a matinee version of its Friday sell-off of last month. But it's a story with a plot twist. This morning, Coinstar reported a near-doubling of fourth-quarter profit, to $0.68 per share. Business is booming, with revenue up 31% and Redbox-specific revs up 38%.

So what: Great news, huh? So why's the stock down 13%?

Now what: In a word: Netflix (Nasdaq: NFLX). Or in two words: digital content. As fellow Fool Rick Munarriz explains in today's column on the Coinstar drop, the world of electronic entertainment is going all digital, all the time. Already, the "Net" carries half the "flix" that Coinstar's rival pumps out. Amazon.com (Nasdaq: AMZN) is thinking along the same lines. Even Electronic Arts (Nasdaq: ERTS) is following Activision Blizzard (Nasdaq: ATVI) with an emphasis on online gaming.

Rick summarizes Coinstar's problem: As revenue growth decelerates from 55% earlier this year, to 31% in Q4, the "once-juicy ... kiosk model is starting to become unhinged." Or more succinctly, Coinstar is just a few kiosks away from becoming Blockbuster.

Will Coinstar turn around, or fall to the ground? Add it to your watchlist by clicking here.

Fool contributor Rich Smith owns shares of Activision. Amazon.com, Activision Blizzard, and Netflix are Motley Fool Stock Advisor picks. Motley Fool Options has recommended a synthetic long position on Activision Blizzard. The Fool owns shares of Activision Blizzard. The Motley Fool has a disclosure policy.

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