Tech investors are a fickle, capricious lot behind only oil traders and buyers of Chinese equities in their lack of forgiveness.

Shares of a bevy of tech companies have been slammed this week, each one previously a darling to a greater or lesser degree. Their transgressions varied, from downright dreadful results to soft forecasts to unexpected tax snafus. What these falling angels have in common is an investment community that sells first and asks questions later.

It’s a good lesson for newer observers of the tech scene: Yes, in fact the lofty valuations of a year or two ago were ridiculous and unsustainable. To have believed otherwise was naïve.

Take GoPro, a fine company with an innovative product its customers love. GoPro’s problem of late is that its newer wares aren’t so great and it has too few customers. It didn’t help that it lowered first-quarter revenue guidance by about $130 million. GoPro is a single-digit stock now, down from more than $65 this summer.

LinkedIn shares were hammered in after-hours trading last night, down 29%, after the recruiting site reported a weak forecast for 2016. LinkedIn has a giant business, but it loses money and it is priced for perfection, as the market mavens say. Now it’s priced for less perfection.

Shares of data-analytics software maker Tableau Software were hit even harder, despite robust revenue growth. The companies shares were off about 36% after hours after it disclosed it was unlikely to benefit as planned from a deferred tax asset. (Fortune’s Andrew Nusca ferrets out the details here.)

This is how it goes. When times are good, problems are easy to overlook. When times are tougher, as they are now, every foible is punished.

***

Recommended reading: New York Magazine has published a gripping and cautionary tale about Ryan Kavanaugh and his film financing and production studio, Relativity Media. During a wave of reporting I did in Hollywood a few years ago I crossed paths with Relativity just enough for this article to resonate. Next time a company’s story looks too good to be true, it probably is.

BITS AND BYTES

Tableau Software plunges after hours. The data analytics company  reported impressive 58% revenue growth last year, reaching $653.6 million and adding 12,500 new customer accounts. But a disclosure about potential tax risks rattled investors. Shares lost close to 40% of their value overnight and hovered just above $50 at the latest check-in. (Fortune)

LinkedIn languishes after loss, revised forecast. The social networking company posted a fourth-quarter loss, and management followed up by significantly reducing its revenue and forecast expectations this year. That depressed LinkedIn's stock by more than 30% in after hours trading to around $133, the lowest level since February 2013. CEO Jeff Weiner said LinkedIn will narrow its focus to "high-value, high impact" initiatives. (Wall Street Journal, Fortune)

Silver Lake, Elliott Management circle Symantec. The cybersecurity company has received $500 million from private equity firm Silver Lake. The money will fund a share buyback, and Silver Lake will receive a board seat as part of the investment. Meanwhile, activist investor Elliott Management is now one of Symantec's biggest shareholders, reports the Wall Street Journal. The company completed its spinout of its data management software division Veritas last week. (Wall Street Journal, New York Times)

So long Google Search Appliance. The company's first product pitched at businesses, a special combination of software and hardware for searching corporate documents, data and information, is being killed. Support for the technology will last through 2019. (Fortune)

Would you bet blind on Uber? High-net worth clients of Morgan Stanley (with more than $10 million in assets) are getting the chance to buy up to $475 million in preferred shares of Uber, but the prospectus for the fund contains very few financial disclosures, reports the New York Times. Merrill Lynch is pitching a similar fund, but it's much smaller. (New York Times, Fortune)

Tech salaries soar as demand skyrockets. After rising a measly 2% during 2014, compensation for tech staffers leapt 8% to an average of $96,370 last year, according to staffing firm Dice. As you might expect, salaries were highest in Silicon Valley. But they've also reached six-figure levels in New York, Los Angeles, Boston, Seattle, Baltimore/Washington D.C., Minneapolis, and Portland, Ore. (Fortune)

PayPal defines its independent identity. The digital payments company is spending big on a marketing campaign that will debut during this weekend's Super Bowl. PayPal is pitching its vision of "new money"—very digital and very mobile. (Wall Street Journal)

Chief Justice Roberts unloads Microsoft shares. Three of the Supreme Court justices—Samuel Alito, Stephen Breyer, and John Roberts—own individual stocks. To avoid a potential conflict of interest, Roberts was recently forced to sell between $250,000 and $500,000 in Microsoft because the court will consider a big case related to defects in the Xbox 360 console. It’s the largest such sale in more than a decade. (Ars Technica)

THE DOWNLOAD

Jive hits back at rivals. The company credited with pioneering “social business” software—a sort of social network for employees—has overhauled its flagship products to make them more “consumer-like.” The transformation is influenced by mobile apps and social networks that people use in their personal lives. Jive's quest is to stay a step ahead of traditional competitors like IBM, Microsoft, and Salesforce while fending off collaboration software rivals like Box and Atlassian. (Fortune)

IN CASE YOU MISSED IT

Atlassian co-CEO stresses predictability by Heather Clancy

Viacom's family feud isn't over by Alan Murray

Apple Pay now accepted at millions of stores by Leena Rao

Cord cutting may be on the rise, but Comcast is holding its ground
by Mathew Ingram

Tech companies shouldn't treat race and gender differently
by Valentina Zarya

Mobile data traffic sent to explode by Barb Darrow

ONE MORE THING

Smart mirror, mirror on the wall. A Google engineer hacked his bathroom medicine. Now he can read the latest headlines and check the weather forecast before hitting the shower. (Medium, Fortune)

MARK YOUR CALENDAR

Spark Summit: Open source data science. (Feb. 16 - 18; New York)

IBM InterConnect: Cloud and mobile issues. (Feb. 21 - 25; Las Vegas)

MarketingSherpa Summit: Advance your campaign and careers. (Feb. 22 - 24; Las Vegas)

Enterprise Connect: Communications and collaboration trends. (March 7 - 10; Orlando, Florida)

Pure//Accelerate: The future of the modern data center. (March 14 - 15; San Francisco)

Next 2016: Google's cloud platform strategy. (March 23 - 24; San Francisco)

Microsoft Build: Microsoft's premier developer conference. (March 30 - April 1; San Francisco)

Microsoft Envision: Where business meets possibility. (April 4 - 7; New Orleans)

Qlik Qonnections: Business intelligence trends. (May 1 - 4; Orlando, Florida)

EMC World: What's next for digital business. (May 2 - 5; Las Vegas)

The Marketing Nation Summit: Marketo's annual conference. (May 9 - 12; Las Vegas)

Salesforce Connections: Cloud marketing trends. (May 10 - 12; Atlanta)

Coupa Inspire: Rethink the possible. (May 10 - 12; San Francisco)

Knowledge 16: ServiceNow's annual service management conference. (May 15 - 20; Las Vegas)

Fortune Brainstorm E: The intersection of technology, energy, and sustainable business. (May 16 - 17; Carlsbad, California)

SAPPHIRE Now: SAP's annual conference. (May 17 - 19; Orlando, Florida)

Gartner Digital Marketing: How to move from vision to execution. (May 17 - 19; San Diego)

Gartner Supply Chain Executive: Creating a value chain. (May 17 - 19; Phoenix)

Google I/O (registration link coming soon): For creative software coders. (May 18 - 20; Mountain View, Calif.)

MuleSoft Connect: Enable your digital transformation. (May 21 - 25; San Francisco)

Inforum: Infor’s annual user conference. (July 10 – 13; New York)

Fortune Brainstorm Tech: The world's top tech and media thinkers, operators, entrepreneurs, innovators, and influencers. (July 11 - 13; Aspen, Colorado)

Sage Summit. For fast-growth businesses. (July 25 - 28; Chicago)

Workday Rising: Talent management in the cloud. (Sept. 26 - 29; Chicago)

Microsoft Ignite: Product roadmaps and innovation. (Sept. 26 - 30; Atlanta)

OracleWorld. The future of the cloud is now. (Sept. 18 - 22, San Francisco)

Dreamforce: The Salesforce ecosystem gathers. (Oct. 4 - 7; San Francisco)

This edition of Data Sheet was curated by Heather Clancy: