I just learned Detroit’s Big Three automakers account for six percent of the revenues of the world’s four largest advertising holding companies. Meaning, if the automakers go down, it will be a painful blow to the firms most responsible for promoting their products. Hmm, let me see if I can work up some sympathy here. Sorry, no can do.

These are the very same agencies that consumed countless barrels of creative fuel bringing us the dream of owning Hummers, Escalades, Expeditions, Yukons, Navigators, Suburbans, Tahoes and other gas-guzzling, climate-killing hogs. I wonder who came up with that delightfully clever idea two years ago by GM to hand out 42 million toy Hummers in McDonald’s Happy Meals and Mighty Kids Meals. Once the kids get their meals, the parents will reach for the toy, and voila, next thing you know they’re with their kids in the Hummer showroom.

The major holding companies — Interpublic, Omnicom, Publicis, WPP — all count a Detroit automaker at or near the top of their list of largest clients. They’ve happily allied with an American industry that Fortune magazine wrote last year has been “getting a free pass on fuel economy for more than two decades. Instead of devoting its considerable technical resources to improving gas mileage, it has been cranking up the horsepower of its engines and selling modified trucks as SUVs.”

And now the Big Three automakers are cranking up the pressure on Congress to bail them out, while the Big Four ad conglomerates hold their collective breath. Detroit automakers are the poster children for environmentally and, now, economically and socially destructive behavior. While the atmosphere warmed, vehicles got bigger. While fuel prices rose, sales of big autos tanked. And while sales disappeared, so did the hopes of local communities whose economies are devastated by auto plant closures.

I’ve seen little evidence any of this has dented the conscience of the world’s leading ad executives. No doubt they’ve been too busy counting profits from their share of the billions Detroit has spent on advertising, including $4.6 billion in measured spending in 2007 alone.

The day of reckoning is now here for big advertising, just as it has been for their auto clients and their clients’ employees and communities. Good folks in advertising, PR and marketing are losing their jobs. My wish is they now find work supporting companies and industries that actually care about our planet’s future.