This week in tech stocks: Why Facebook nosedived

Facebook was on fire this week — not in the Sherman-does-Atlanta sense, but in the Katniss-from-Hunger-Games sense. So why did its stock tank?

This week, Facebook posted a truly stellar earnings report. Revenue was up by 64 percent, and profits rose to nearly a half-billion smackers. And on mobile — social media’s most important platform — we learned that the company is closing in on an unprecedented billion active users.

And its stock price is down around 8 percent for the week. Say what?

As our own John Koetsier explains, twelve little words from the investors’ call were enough to seal the deal: “We did see a decrease in daily users specifically among younger teens.”

That quote from Facebook CFO David Ebersman was, if not a death knell, certainly a pummeling-knell.

More earnings-related movement: Apple posted an amazingly forgettable $171 billion in revenue for fiscal year 2013, a number that’s totally unsustainable. Investors responded with a -.26 vote of “meh” confidence.

Comcast highlighted the success of its video-on-demand offerings and saw a nice 3 percent lift. Also on the media side, Netflix reported 40 million subscribers, proving its focus on original content focus is paying off, but investors were squeamish, leading to a 7 percent tumble.

The real stars for the earnings season were Brightcove, which experienced a 6 percent incline post-earnings, and Amazon was up 10 percent, thanks to steady growth and in spite of a few important but unanswered questions.

Here’s a look at the stock price movement in percentages:

AAPL data by YCharts