The No. 1 reason to fear a Letterman mention

Having your brand mentioned on David Letterman's show is usually a marketer's equivalent to winning the lottery. But Jamba Juice may have a different valuation after being discussed at length during a broadcast aired last week and preserved on countless digital recorders, including mine.

All initially went well, with Dave lauding the chain's smoothies and acknowledging that he's an enthusiastic customer. He also noted how much you get for your money, vertically spreading his hands by at least a foot in an exaggeration of the serving size. And that's when the plug "gunny-sacked," to use his synonym for a train wreck.

The problem, he quipped to sidekick Paul Schaffer, was a tendency to suck it all down. It'll bloat you up like a Thanksgiving Day Parade balloon, he asserted, noting that he'd already cut down his usual order from two cups to one.

Within minutes, Letterman was suggesting the chain change its name to Jamba Bloat, and recommended that it print an alert on its cups: "Warning, could cause bloating."

His discomfort became a running gag during the show, leading to the exclamation at one point that his liver was being shoved against his pancreas. He also took to chanting "Jamba" to Tina Fey, his first guest, as she described a noxious-looking and nauseating potion that she quaffed daily as an energy potion.

There is no such thing as bad publicity, according to the old adage. But the performance was a veritable Top 10 List of why that maxim should bear an asterisk.