The engine behind General Motors' (NYSE:GM) new mystery ad campaign stalled out as techies quickly cracked the secret code. No, "GM" certainly does not stand for "great mystery."

The GM ad campaign was envisioned to keep everyone guessing as they tried to crack the code and solve the secret message -- "A message so important we need the whole country to tell it," GM said on a related site. In other words, billboards with one word of the puzzle -- in New York City, just a period -- were to appear across the country, so that people from coast to coast would theoretically be fascinated as they sought to guess the secret message.

Getting people's minds to puzzling may be a great idea in advertising, in terms of making them stop and dwell on their products. (However, it's certainly not a new idea: An entertaining example is Ralphie's dismay in the movie A Christmas Story when his long-awaited Little Orphan Annie decoder ring revealed a message that simply entreated him to "Be sure to drink your Ovaltine.")

While GM's idea was clever, there was one fatal flaw. GM left the crux of the message in the source code on the website related to the ad campaign, for anyone with a bit of technical knowledge to read. This means that, despite what it said, GM doesn't need even half the countryside to tell it -- it's been released on the Web.

According to several news sites, the message read, "This is the last time you will ever have to feel alone on our nation's roadways." (Those of us who live in high-density cities and suburbs might joke that we never feel alone on our nation's roadways, period. But I digress.) Think OnStar, the navigational and communications system that is likely going to be a feature in all GM cars.

The spirit of the advertisement certainly jells with corporations' recent attempts to go a little extra mile in advertising reach, given the fact that many people are skipping traditional TV advertisements using technologies like TiVo (NASDAQ:TIVO). Product placement deals have come to have a new emphasis (this is not lost on GM, which was the company involved in this lark on Oprah), and some advertisers are trying new experiments with TiVo itself to try to grab people's attention from the increasingly popular fast-forward button.

So, GM's puzzle is spoiled; does this ruin the ad? Although it kind of takes the extra sparkle out of the ad and makes GM look more than a bit silly, it is now simply relegated to any traditional billboard advertising campaign. (There is apparently another line that people can figure out, but it seems that really, the cat is out of the proverbial bag.) The core message remains intact, with certainly less impact than was originally intended -- or, maybe, budgeted for.

Next time, though, GM, keep that kind of spirit in advertising to spark some interest in prospective buyers, but bear in mind -- people are smarter than you think.

For more on General Motors, Ford (NYSE:F), and DaimlerChrysler (NYSE:DCX), see these articles:

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Alyce Lomax does not own shares of any of the companies mentioned.