It seems absurd in retrospect, but there was a time not that long ago when young cellphone owners would pay not-insubstantial amounts of money for ringtones. That is, they’d spend money to change the sound their phone made when someone called them, usually to a popular song. (This was an era when people still let their phones ring.) Ringtones were a fun, mostly harmless auditory accessory to the first era of cellphones, but they resulted in staggering cellphone bills for some parents. Children would buy ringtones with reckless abandon, racking up hundreds of dollars in extra cellphone charges. According to an article published by CNN, U.S. ringtone sales went from $68 million to $600 million from 2003 to 2006, a nearly ninefold increase.

Ringtones would prove to be a short-lived phenomenon; just a few years later, the market would be a fraction of its former size, as the novelty of the song snippets wore off. But the rise and fall of ringtones can teach us an important lesson about the importance of customer consent—a lesson the digital advertising industry would be wise to learn from as it enters an era of digital integrity.