Not sure I fully understand this, but interesting. Seems they'd be able to track popularity and how viral something is relative to it's original source, but getting it down to the individual user would be difficult and/or expensive.
Could Audio Watermarking Help Make MP3s Free?
Audio watermarking involves taking a song and manipulating it digitally to create an audio pattern that is unmistakable to the right software -- such as Activated's -- though undetectable by human ears.
The tracking technology allows advertisers to gather information about the consumer and the effectiveness of the ad. Such data, according to Silberstein, is so valuable that advertisers would be willing to pay five to 10 times rate of a regular ad for an watermarked ad. That data works particularly well with "call-to-action" type of ads, in which consumers, after listening to an ad, respond or click on a link to buy something or otherwise opt in to the advertiser's campaign, Silberstein said.