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. AT&T is TNT backwards
AT&T (NYSE: T) has had it with iPhone data hogs. It will stop offering unlimited data plans on new smartphone -- and iPad -- contracts next week. Existing customers on unlimited plans will be grandfathered in until their deals run out.

This is a dumb move, on many levels.

Let's start with how this will hurt AT&T. Current customers paying $30 for unlimited data can now trade down to cheaper $15 and $25 plans that cover 200 megabytes and 2 gigabytes of bandwidth, respectively. The carrier claims that just 2% of its smartphone accounts were averaging more than 2 gigabytes a month, so it would seem to make economical sense for the vast majority of AT&T's users to trade down to cheaper plans. Who won't trade down? Duh. The heavy data eaters will keep noshing away.

Now let's get to Apple (Nasdaq: AAPL). It has been pricing its 3G iPad at a $130 premium, pushing a $30 unlimited data plan from AT&T that no longer exists. This is a device that is built for streaming chunky multimedia files. This will now be metered, unless someone is on a Wi-Fi connection.

Is that safe from the meter maids, though? If other wireless carriers begin to follow AT&T's lead, it won't be long before consumer broadband follows suit. For those scoring at home, that's the Wi-Fi connection that has been keeping you off of AT&T's 3G network.

The smorgasbord is ending, and that's going to have rippling and crippling impacts on general Internet usage, video streaming, and smartphone migration rates.  

2. BP is both junk and shot
Shares of BP (NYSE: BP) began the holiday-shortened trading week with a 15% hit on Tuesday, after its latest efforts to cut off its underwater oil spill came up lame.

BP's shares have coughed up more than $60 billion in market capitalization since the oil rig explosion on April 20 that started this environmental disaster. Some may argue that the sell-off is overdone, especially given the $7 billion in cash on BP's balance sheet.

I don't see it that way. This is about more than the billions -- or tens of billions -- that BP will be on the hook for in cleaning up the mess for which it may only be partly to blame. There will be ramifications beyond the widening slick.

There are "Boycott BP" groups on Facebook amassing hundreds of thousands of fans. There's a spoof Twitter account that is far more popular than BP's actual stream. The petroleum giant is trying to take control of the message by promoting its YouTube channel, but has been doing so with viewer comments turned off. Information -- like renegade oil in the gulf -- apparently only flows one way in BP's world.

The BP brand is shot. The court of social networking -- that didn't exist during the Exxon Valdez incident -- has spoken. A buyout as a way for drivers to return to BP-affiliated gas stations under new signage may be the only way out.

3. Every sunrise is followed by a sunset
It was lights out for Canadian Solar (Nasdaq: CSIQ) this week, after an SEC subpoena forced the Ontario-based solar energy company to postpone its quarterly conference call.

Before the subpoena was issued, Canadian Solar appeared to be in pretty good shape. Most of its peers that have stepped up during earnings season have delivered substantial bottom-line improvement over last year's showings. However, now the company is launching an investigation to address SEC concerns about certain sales transactions that were recorded late last year.

Canadian Solar is advising shareholders that it may have to revise last year's financials if the SEC claims are valid.

4. Cheap chic rekindling
Amazon.com (Nasdaq: AMZN) will begin selling its Kindle e-book readers in Target (NYSE: TGT) department stores on Sunday.

It seems as if it's too little, too late. Forget the fact that $259 ticket items are rare at the cheap chic retailer. There is just a little correlation between success as an e-book reader and having a bricks-and-mortar presence. Nook and Reader gadgets have been available through stores for as long as they have been on the market, and it doesn't seem as if hands-on access is a meaty driver of new sales.

Amazon's push outside of its e-tail hotbed also comes too late. Why now? Why didn't it step up before Apple's iPad hit the market two months ago?

5. Pay less for Payless
May wasn't all that bad at the mall, as retailers posted a 2.5% spike in same-store sales. There were a few chains posting negative comps -- mostly trendy teen magnets that have fallen on hard times -- but it seems as if most of the stores giving cost-conscious consumers more bang for their buck are doing OK.

Well, then we have Collective Brands (NYSE: PSS). This is the parent company of Payless ShoeSource. The name says it all. Who doesn't want to pay less for shoes? Well, Collective Brands' stock cooled off this week, after the company posted healthy bottom-line growth but a 2.2% slide in same-store sales, excluding the impact of foreign exchange rates.

Really? We're buying fewer cheap shoes now? Collective Brands' shares fell 7% on Wednesday after the report. I guess investors can "pay less" now, too.

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

Apple and Amazon.com are Motley Fool Stock Advisor recommendations. Try any of our Foolish newsletter services free for 30 days. That certainly wouldn't be a dumb move.

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.