AT&T is up to some dirty wireless tricks these days, sending text ads to a “significant number” of its own customers. The ads were meant to remind customers to tune in, turn on, and text their votes away for American Idol, a show which the wireless firm is a sponsor of. Although the texts are free, users who vote for their favorite Idol contestant via text are charged a text fee and a voting fee.

According to the NY Times, because AT&T allowed customers to opt out of Idol text ads, the firm was acting within the constraints of the law: Claudia Bourne Farrell, a spokeswoman for the Federal Trade Commission, said the message had not appeared to violate the commission’s rules or the law. It would do so only if it cost recipients or was deceptive in some way, and did not allow recipients to turn off future messages.

Because the law is so vague, it is unclear what “opting out” really means. Does opting out mean that you opt out of Idol text ads and all other text ads regarding all other advertisers in the future? Or does that mean that as a customer you only opt out of just Idol ads? If it’s the latter, then prepare yourself to constantly try to opt out of ads on your phone. Perhaps the US government needs to setup a “Do Not Text” registry similar to the existing Do Not Call database.

AT&T may be paving way for other wireless carriers as well with this “trial” for SMS ads.

Disclaimer: For what its worth, I am an AT&T customer and I was not part of the “significant number” that received an ad via SMS for American Idol.