Did Silicon Valley just disappear in a massive sinkhole?

That's what it looks like today, anyhow. The Dow Jones Industrial Average (DJINDICES:^DJI) is down 0.7%, led by the storied index's tech giants. The tech-heavy Nasdaq (NASDAQINDEX:^IXIC) fell 1.4%, or twice as hard.

Intel (NASDAQ:INTC) is by far the Dow's worst performer, down 2.7% on a rare sell recommendation from Wall Street firm Bernstein. The firm worries that Intel's phenomenal success in recent years came from unsustainable pricing power and that margins will collapse very soon.

But the tech sector's pain doesn't stop there. Apple (NASDAQ:AAPL) is down 0.04%. Microsoft (NASDAQ:MSFT) fell 1.7%, while Google (NASDAQ:GOOGL) is down 1.45%. Tuesday's tech malaise is widespread. These four stocks alone erased more than $17 billion of shareholder value overnight.

And some of these drops fly in the face of today's market-moving news. Apple should be soaring as details about its rumored iPad Mini trickle out. Microsoft investors might wear their nerves on their skin as next week's earnings report approaches, but then, Mr. Softy is also gearing up for the crucial launch of Windows 8. Google is also preparing another earnings report and has no bad news of note to worry about.

Many Dow stocks are dropping on yet another round of global economy warnings. But you would expect megabanks and heavy construction companies to take the brunt of that action. That's not what happened here.

This could be a rocky earnings season for tech investors. The sector is rebuilding itself with a brand-new mobile focus, but nobody knows how deep consumer hunger really runs for tablets and smartphones. Hold on to your hats and watch these bellwethers with a wary eye over the next few weeks.

Fool contributor Anders Bylund owns shares of Google. The Motley Fool owns shares of Apple, Google, Intel, and Microsoft. Motley Fool newsletter services recommend Apple, Google, and Intel. Try any of our Foolish newsletter services free for 30 days. 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 has a disclosure policy.