Look, we’re all under stress. On the personal front, our 401Ks are MIA and our home valuations have put an unfortunate new spin on the phrase “sweat equity.” Meanwhile our workplaces are pressure cookers, with bankruptcy filings, layoffs and salary freezes. (Not here at Promo, of course. We still keep a basket of benjamins by the coffee maker for lighting our lunchtime Cohibas.)

The point is, we as a public are getting cranky, and we may be less prone to put up with some of the things we found fun in 2007 or at least tolerable last year. And that seems to have been part of AT&T Wireless’ miscalculation in firing out text messages to “a significant number” of its 75 million user base, reminding them to tune in to the Tuesday night launch of the eighth season of “American Idol” on the Fox Network.

According to press reports, the messages were sent as a “friendly reminder” and went out mainly to AT&T Wireless customers who had in the past been heavy text voters on the program. AT&T customers are the only mobile audience members who can text in votes, and in the past they’ve done so extravagantly. The carrier claims that last season’s audience sent 78 million text messages to the show in the course of the season. Nielsen Mobile has estimated that “American Idol” fans sent in an average of 38 SMS to the show last year.

In the face of that kind of exuberance, it was perhaps understandable that AT&T would want to remind those past viewers that their favorite was back. After all, the carrier makes a substantial revenue stream from people casting cotes for their singing picks.

But let’s face it. The fans of the show probably didn’t need to be reminded of its return, judging by that SMS traffic load for the previous season. And the rest of us just don’t care.

And that may have been AT&T’s most crucial misstep. The Times article points out that the messages didn’t just go to people who had texted “Idol” in the past but also to other “heavy texters.”

Big mistake.

Text messaging has grown so popular, both for business communication and for social purposes, that that heavy-user contingent now probably includes lots and lots of subscribers who would sooner cut a check to that deposed Nigerian leader who’s always in need of ready cash than watch “American idol.” So lumping these folks in with the “Idol” crowd was a serious misread by AT&T of the market for its service.

And the people who felt pestered by the messages weren’t shy about complaining about them, on Twitter and in blogs.

“AT&T is now sending me unsolicited text messages advertising the new season of American Idol,” wrote spencerholleman. “What did I do to deserve this?”

Waltrupar: “Are you kidding me AT&T? Please don’t send me SMS spam. Especially if it’s about American idol!!”

5tu: “I just spent 13 minutes on the phone with AT&T explaining that I will cancel my service immediately if I receive an American Idol spam txt.”

And from adamisacson: “9:06AM. A text message now? Did I miss an urgent meeting? Is it the kid’s preschool? No. AT&T needs to tell me about American Idol. Die.”

It’s natural that in a down economy, marketers are going to want to push the envelope, and AT&T probably assumed it was a wise move to prime the AI pump with a handy little kick-off message. But firing that ad out to people who had not taken part in “American Idol” voting was a mistake.

Mobile marketers in particular are going to have to be wary of improperly targeting their messages as the SMS user base grows far beyond the initial group of teens and tech-heads. Surveys have suggested that cellphone users are willing to accept mobile ads that they consider relevant.

But some of those surveys also show that users are far, far more willing to accept ads if they get something in return, such as free minutes or enhanced mobile service. That indicates to me that for many of them, ad acceptance is grudging at best.

And mobile marketers can turn them off quickly if they send irrelevant, poorly targeted or improperly permissioned text ads out. A mobile phone is a particularly personal device—much more so than a PDA or a laptop. Spam sent over a mobile phone can make users feel much more vulnerable than that coming into an e-mail box.

The AT&T “Idol” messages weren’t spam by definition: They were free and included clear instructions for opting out of further messages. But they were irrelevant to some portion of their recipients, and that’s the primary criterion most people use for judging a message, either e-mail or text, as spam—no matter what the industry definition of the term may be.

With privacy watchdog groups calling for a Congressional investigation of the mobile ad industry, this is not the time for carriers to be stirring up anti-ad sentiment among any portion of the public.

It’s an interesting question whether a marketer who wasn’t also carrier would have been able to market to so wide a group of phone users. In the past, the wireless carriers have had a culture that made it difficult to send a message out to large swathes of the mobile population on the assumption that it would be irrelevant and irritating to some portion of that group. The carriers used the justification that they were looking out for their ultimate customers, the subscribers.

Good thinking. AT&T should have exercised it in this case and seen the risk inherent in shotgunning these text ads way beyond their audience.