When President Obama made a joke about Special Olympics on "The Tonight Show" last week I cringed. The man has a lot on his mind, of course, but common sense should dictate instantly that some subjects simply aren't joke material.

A thousand mental red flags should have been flapping wildly before the president lamented that his low bowling score "is probably like Special Olympics or something."

Mr. Obama apologized and I agree with those who say let's move on. Still, the episode got me to thinking about common sense -- or the lack of it.

I like the Merriam-Webster Dictionary definition of common sense: Sound and prudent judgment based on a simple perception of the situation or facts.

In Mansfield, Ohio, where I work as the public relations director for the area's largest public school district, I often walk past a former downtown bank building. Built into the stone facade near the entrance is a cast-iron drum for night deposits which has long since been sealed shut. There on the handle -- in raised letters just as the drum came from the foundry decades ago -- are these words: Remove hand before closing.

Apparently, the bank feared that some folks might not arrive at the simple perception that shutting one's hand inside the cast-iron drum might be painful.

My travels sometimes take me over a railroad crossing where a sign warns: No stopping on tracks. Who would want to? I always think to myself.

The state department of transportation obviously believes that some drivers must be reminded that stopping their vehicle on railroad tracks could result in it being rammed by a train.

Some warnings that fly in the face of common sense are meant to reduce liability and the threat of lawsuits. That's why our fast-food coffee cups caution that the contents are hot.

Remember the 79-year-old woman who was seriously burned by a cup of McDonald's coffee several years ago? The jury that awarded her a huge settlement determined that the coffee served at the drive-through was more than hot -- it was scalding. But jurors also said the woman, a passenger in the front seat of a car, was "20 percent at fault" because she had placed the coffee between her knees and was trying to remove the lid when it spilled.

Translation: The lack of common sense was 80 percent McDonald's and 20 percent the woman's.

Among my favorite common sense issues are the television commercials in which new car dealers proclaim, "We're selling them below invoice!" The implication is that the dealer will sell you a car for less than he paid for it. When common sense fails, some don't stop to question how he could lose money on car sales and remain in business.

Who are the first folks to rush down to that dealership? The same ones who would close their hands in the night-deposit drum or stop on railroad tracks.