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. Maybe it's just you, Yahoo!
One of the downers in Yahoo!'s (Nasdaq: YHOO) bland quarterly report this week was a 7% decline in search advertising on its owned and operated websites.

Yahoo! is in the process of handing its engine and paid search functions to Microsoft's (Nasdaq: MSFT) Bing, and it's going to be an area to watch. Yahoo! is growing reasonably in display advertising, so what's the dot-com giant's excuse for coming up short -- just a few days after blowout results from its larger rival?

"[A]s users experience fresher and more relevant results on Yahoo! search pages powered by Microsoft, they clicked more on the organic results and less on the paid results," CFO Tim Morse told analysts on the call.

In other words, Bing's search engine results are so good that folks aren't bothering to click on the sponsored results. Some things would confirm this, such as flat search query growth and lower page volume (so users are finding what they want sooner).

However, here's another possibility, Morse. Maybe it's not the search results that are good. Maybe it's the sponsored ad inventory that's bad.

Boom! I just dealt Yahoo! a blast of purple haze.

2. Palm someday
(NYSE: HPQ) spent $1.2 billion on Palm earlier this year. Did you think it was just going to park it in Jay Leno's garage and walk away?

HP is finally giving the Palm Pre another go. It begins selling the Palm Pre 2 in France today. A stateside rollout will follow in the coming months. HP is also rebooting Palm's webOS, adding new features and building on the multitasking prowess that turned heads initially with the first Palm Pre last year.

Is it cool that HP has a proprietary operating system in webOS to market? Maybe, but it's going to be an uphill battle for HP. Not only is the company without its popular CEO that was the architect of the Palm purchase, but the market has gotten even more crowded in Palm's brief absence.

We're surrounded by BlackBerrys, iPhones, and Androids. WP7 is diving in with several partners already onboard.

Sorry, HP. I like the outfit, but you're just too late to the party.

3. By hook or by Nook
If Palm Pre 2 is a questionable move, Nook 2 sounds like a recipe for e-reader disaster.

Barnes & Noble (NYSE: BKS) is scheduling a media event for next Tuesday. More than likely, it will be an updated Nook.

Why not? It's now been a year since the leading bricks-and-mortar bookseller introduced its e-reader. The company isn't divulging how many Nook readers it has sold in its first year, but have you ever seen one in the wild?

I didn't think so. The Nook raised the bar with some interesting wrinkles last year -- just as the Pre did. However, both products suffered as a result of the financial limitations of its parent company.

How can B&N market the Nook appropriately when analysts don't see it turning a profit until fiscal 2013 at the earliest -- if it even gets that far.

Hey, HP! Are you in the market for a book superstore chain?

4. Executing executives
Shares of Christopher & Banks (NYSE: CBK) took a 14% hit on Wednesday after announcing that both the company's CEO and its chief marketing officer had left the company.

Yes, that's bad -- and so is the fact that the struggling retailer's CFO bolted during the summer.

No one wants to run the company, stock its stores, or run the numbers? Maybe they took the "everything must go" sales sign seriously.

Christopher? Banks? Bueller? Anyone?

5. The sun sets
After scorching returns and generally hot blowout quarters in recent weeks, solar energy stocks fizzled out earlier this week.

JA Solar (Nasdaq: JASO) and LDK Solar (NYSE: LDK) fell 10% and 14%, respectively on Wednesday. Fears that a higher yuan will make it more expensive for Chinese manufacturers to export their wares and accusations that China's government is subsidizing the industry rocked the market darlings.

Nothing goes up forever, but these knocks are overblown. A lot of solar panels are going up in China right now, so currency fluctuations and outsider opinion aren't necessarily deal breakers.

Despite the gains leading to Wednesday's fall, both stocks are surprisingly cheap. JA Solar is fetching just eight times this year's earnings!

Silly sellers.

Which of these five moves do you think is the dumbest? Share your thoughts in the comment box below.

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Longtime Fool contributor Rick Munarriz is a fan of dumb and smart business moves. Investors can learn plenty from both. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.