Are free-texting apps legal?

Free-texting apps enable you to send messages for free. But is there a catch?

Back in 2009, on a lark, two friends in Pennsylvania decided to try to set a world record for sending the most Short Message Service (SMS) text messages. In the course of a month, they thumbed their phones energetically, transmitting an astonishing 217,000 texts. "A lot of times it was 'hey what's up,' 'how are you doing,' 'what's up,' 'hahaha,' 'lol,' over and over again," one of the men later explained to ABC News. It was great fun, until one of the pair was shocked to receive a bill from his mobile carrier for $26,300 [source: Mayerowitz].

Fortunately for him, the company agreed to tear up his bill. But that story is a reminder of the downside of SMS texting, which Americans love so much that they now send and receive more texts than the number of minutes they spend talking, according to a 2011 Nielsen survey [source:]. In an age when most other popular forms of electronic communication -- e-mail, social networking sites like Facebook and Twitter, instant messaging apps, the video-chat service Skype -- are available for free, mobile phone carriers still charge for texting, sometimes as much as 20 cents per message you send or receive [source: Wortham].

Or rather, that's what you have to pay if you don't have a "free-texting" app. Today, if you have an Internet-connected smartphone, you can take advantage of a growing assortment of downloadable apps that allow you to send and receive messages without incurring carrier charges, usually by bypassing the carrier's SMS system and sending messages through the Internet. One such app, Pinger, has become so popular that it handles more than two billion messages a month, and its eponymous San Jose, Calif.-based corporate parent has become the seventh biggest data carrier in the nation [source: Delevett].

Free-texting seems like a no-brainer for phone users -- so much so, in fact, that mobile phone service companies have been wailing and gnashing their teeth about the ruinous competition, and they're even contemplating giving up on the old charge-per-usage plans that have long have been an industry cash cow. But you may be wondering: How do they afford to let you send texts for free? Is it even legal? And is there some hidden catch to what seems like a something-for-nothing deal?