• by Wendy Davis , Staff Writer @wendyndavis, August 2, 2012

Here's some unsettling news for mobile marketers: Sixty-nine percent of mobile phone users who text say they receive spam, with one in four text users receiving spam at least weekly.

That's according to a new report from the Pew Internet & American Life Project.

One reason why those findings could spell trouble for marketers (and their agencies) is that the federal Telephone Consumer Protection Act gives people the right to sue -- for up to $1,500 per incident -- when companies use automated dialing systems to send them unwanted text ads.

Such lawsuits have proliferated since 2009, when the 9th Circuit Court of Appeals ruled that Simon & Schuster potentially violated federal law by allegedly sending unsolicited text messages promoting Stephen King's "Cell."

That ruling marked the first time that an appeals court said that text messages were covered by the Telephone Consumer Protection Act. But in the three years since then, numerous other courts followed the 9th Circuit's lead and allowed lawsuits against mobile marketers to proceed.

In the latest example, two weeks ago U.S. District Court Judge Janis Sammartino in the Southern District of California ago rejected Microsoft's argument that a text-spam lawsuit should only go forward if the consumer who sued could show an economic injury. Sammartino ruled that the federal prohibition on text spam allows people to sue regardless of whether they had to pay extra to receive the messages.

At the same time, not every case has gone against marketers. Taco Bell recently prevailed in two separate text-spam lawsuits. In one case, a federal judge ruled that Taco Bell didn't violate the law by sending a single text to a user who had opted out; the text was to confirm that the user no longer wished to receive future messages.

In the other Taco Bell matter, a federal judge ruled that the company wasn't responsible for text messages allegedly sent by an agency. A group of 12 local franchisees had hired the agency, but a division of Taco Bell appeared to have paid for the campaign, according to the court papers.

Of course, not all spam campaigns will lead to lawsuits -- especially because it's not always obvious who sent the ads. "Plaintiffs' lawyers tend to go after those with deep pockets, and at least some of the spam is tough to easily connect to anyone," cyberlaw expert Venkat Balasubramani says in an email to MediaPost. He adds that text-spam that isn't clearly linked to particular marketers hasn't so far resulted in much litigation.