Stupidity is contagious. It gets us all from time to time. Even respectable companies can catch it. As I do every week, let's take a look at five dumb financial events this week that may make your head spin.

1. LinkedIn doesn't get the job done
LinkedIn (LNKD.DL) nailed its quarterly job review last night, but then it tripped on the way out.

There's no denying that the social business networking site is on a growth tear, and its streak of delivering market-thumping quarters explains why the shares raced to an all-time high just minutes ahead of Thursday's report.

LinkedIn did deliver a strong quarter. Revenue rose 72% to $324.7 million. Adjusted earnings per share tripled to $0.45. Wall Street was settling for an adjusted profit of $0.30 a share on $318 million in revenue.

However, then came LinkedIn's guidance. Forecasting $342 million to $347 million in revenue for the current quarter is short of the $360 million that the pros were targeting. Its full-year outlook also falls short, and that's with the first quarter blowout padding its performance.

Better luck next interview, LinkedIn bulls.

2. ZAGG sags
ZAGG (ZAGG) may want to come out with an invisibleSHIELD product for its stock certificates. Bulls could use it about now.

The company behind the protective film covering for smartphones and tablets posted shockingly bad quarterly results after Thursday's market close.

Sales declined 7%. Analysts were forecasting a 20% surge on the top line. ZAGG's adjusted profit of $0.11 a share is roughly half the $0.21 a share that Wall Street was expecting.

"This was a uniquely challenging quarter," its CEO begins to explain -- but no one's sticking around to hear the rest of what he has to say since they're too busy running for the exits.

3. Take two tablets and call me in the mourning
Just as I was taking Microsoft (MSFT -2.45%) to task for having to give away thousands of concert tickets to get young people to care about its new store opening in Miami -- boom -- Mr. Softy announces more free shows.

  • Macklemore & Ryan Lewis and Neon Trees will play a free show for a new store in Hawaii on June 13.
  • Weezer will play a free show for a new Illinois store on June 22.
  • Kelly Clarkson will pay a free show for a new Michigan store on June 28.

However, since many will argue that Microsoft is doing a "smart" thing by tricking hipsters to line up at its grand openings, let's go with how poorly its Surface tablets are faring.

Industry tracker IDC is reporting that Microsoft shipped just 900,000 Surface tablets this past quarter. Despite the onslaught of Surface ads, the software giant shipped half as many Surface tablets as Kindle Fires with minimal marketing.

Maybe Microsoft doesn't belong in the tablet hardware market.

4. The sun rises early
SunPower (SPWR -3.09%) delivered a blowout quarter yesterday.

SunPower's adjusted profit of $0.22 a share on $575 million in revenue blew away Wall Street projections for income of $0.10 a share on $510 million in revenue.

Why does this blowout report make the "dumb" list? Well, SunPower's earnings presentation materials leaked early, giving quick-acting speculators and investors the ability to buy into SunPower with minutes left in the trading day. SunPower shares naturally spiked on the premature reveal.

This isn't the first time that a report has surfaced online ahead of its actual scheduled release. It probably won't be the last time.

5. Return to sender
Pitney Bowes (PBI -0.47%) took a hit after slashing its dividend.

Was this really so hard to see coming?

The metered mail business has seen its revenue and profitability sliding for some time. Did income chasers really expect Pitney Bowes to keep its chunky yield forever? After it increased its rate in each of the previous 30 years, surely investors had to know that the streak was endangered. You can't grow your distributions if your fundamentals are going the other way.

Get smart
You may have followed some losers this week, but there's always time to get it right the next time.