There is an old humor maxim that tragedy plus time equals comedy. It's why we can laugh at the joke "other than that, how did you enjoy the play, Mrs. Lincoln?"

But it's hard to see a mainstream joke about the Sept. 11 attacks, for example.

The folks at Groupon ignored that comedy rule in what was the worst commercial of Super Bowl XVV, the Internet coupon company's first foray into the most closely watched collection of TV spots (Yes, there were actually people who watched Sunday's game for something other than the action on the field).

Here's Groupon's spot:

Opening like a public service announcement about the plight of Tibetans under Chinese oppression, it turns into an ad that virtually mocks the ongoing tragedy.

Yes, it gets people talking about Groupon (and maybe even Tibet), but the on-line anger that started flowing after the ad aired is not what a business wants. That's especially true in a business with the "Internet cool" veneer of Groupon. It can't lose the cyber-crowd.

Groupon stood out negatively in a pretty forgettable crop of Super Bowl ads. On the positive side, the only ad that really surprised me was Chrysler's long, but beautifully shot ode to Detroit:

The message may have not been totally upbeat, but it was resolute and strong and hopeful. And Detroit never looked better.

For me, two other spots rose about the mundane. I liked Faith Hill's Teleflora spot:

I also liked Volkswagen's "Black Betty" spot.

The automaker's Darth Vader spot was so thoroughly distributed in advance on YouTube that it seems like a waste of money to buy the ad time. But this spot for the Beetle was a pleasant surprise:

There was much talk in advance about the Doritos and Pepsi Max spots (and they scored well in USA Today's Super Bowl Ad Meter. Frankly, I found them pretty forgettable. A winning Super Bowl ad should survive beyond the initial laugh they give go. And there was an oddly violent theme to some of them, like this Pepsi Max spot:

There was another Pepsi Max commercial featuring a can lobbed into a guy's crotch. Is that a marketing theme?

I also don't get the appeal of this Doritos ad:

Funny, yeah. But it doesn't exactly make Doritos seem all that appetizing.

But the bottom line is that it was a lackluster crop of ads, with a lot of over-produced spots that did little to sell the product.

At least there was enough action on the field to keep us watching to the final minutes.

I'll be talking Super Bowl ads with Gene Purcell at 5 this afternoon on the Ideas Network of Wisconsin Public Radio, WHAD-FM (90.7) in Milwaukee.

And feel free to comment with your best and worst ads of the big game.

Aaron, meet Dave: Quarterback Aaron Rodgers goes swiftly from Dallas to the New York to visit David Letterman tonight at 10:35 on Channel 58. It's the seventh year in a row that the Super Bowl-winning quarterback visited the show.