It always turns heads when a CFO leaves a company, so Netflix (Nasdaq: NFLX) had to know that last night's announcement that CFO Barry McCarthy would be leaving wouldn't go over too well with investors.

It also doesn't help that McCarthy exercised a ton of stock options last month, selling more than $40 million worth of Netflix stock along the way.

As the chief bean-counter at Netflix, does his departure hint at the mother of all accounting scandals? No. Grow up. Executives leave all the time. However, McCarthy is leaving just as the stock is hitting all-time highs. Netflix's stock has more than tripled this year alone.

In other words, he's picking an opportune time to cash out as he seeks a change of scenery.

Jefferies & Co. analyst Youssef Squali thinks shareholders may want to follow suit. Squali downgraded Netflix stock from buy to hold after the company announced McCarthy's departure.

McCarthy wasn't just some mercenary executive. He's been with the company since its early years, and proved instrumental in taking the company public eight years ago. The press release claims he's off to pursue "broader executive opportunities;" he clears out his desk Friday.

These are interesting times for Netflix. The company has grown quickly. It now watches over 16.9 million subscribers, trailing only Comcast (Nasdaq: CMCSA), Sirius XM Radio (Nasdaq: SIRI), and DIRECTV (NYSE: DTV) in premium entertainment subscribers. By this point next year, I wouldn't be surprised to see it leading all three.

However, the competition is finally starting to smarten up. As I pointed out yesterday, Apple and are beginning to take digital video seriously.

Apple is trying to woo customers by sending out online coupons for free iTunes movie rentals to select accounts this week. is reportedly working on a streaming service that it will bundle with its loyalty shopping program. Studios are also starting to bellyache over Netflix's growing power.

Maybe McCarthy sees that the competitive landscape is changing. The more likely scenario, though, is that he also realizes that his stock as a key executive is also at an all-time high, after helping to guide Netflix through years of market-thumping performance. If he wants to be a CEO elsewhere -- an opportunity he will never get at Netflix, unless Wall Street fave Reed Hastings decides to make the leap into politics -- why not strike while the iron is hot?

McCarthy's move makes perfect sense -- but the market's disappointment today is equally understandable.

Which rival offering makes Netflix the most vulnerable? Share your thoughts in the comment box below.