Feb 14, 2014 · 2 minutes

We all know music taste can speak volumes about a person's identity. Science supports this: One study found that music preferences reveal more about personality than television tastes, film tastes, and book tastes. In fact, music tastes revealed only slightly less about personality than the "Hobbies and Activities" a person enjoys.

This presents a unique opportunity for music startups like Pandora and Spotify which, despite attracting millions of users, have struggled mightily with profitability. Spotify has never been profitable. Pandora, while posting positive earnings last quarter, has yet to prove it can sustain those profits. Subscription fees help, but both companies will need to boost their ad revenue to survive. If these companies can predict what users will buy or who they will vote for by their taste in music, that's a very attractive carrot for not only advertisers, but political operatives as well.

That's why Pandora will launch a new ad service next week that allows political campaigns to target users based on what they listen to. For example, if a Tea Party Republican like Ted Cruz wants to reach his core constituency, he may target listeners of country star Brad Paisley. If Democrat Elizabeth Warren wants to ramp up support for a possible 2016 bid, she may go after Miles Davis fans or Skrillex fans (probably not a lot of overlap there, but both genres skew Democratic according to Pandora).

These insights may sound obvious. And indeed Pandora even admits to the Journal that it struggles to classify hip-hop and classic rock which enjoy bipartisan support. But throughout its 14-year history Pandora has collected massive amounts of data on listening habits to build detailed user profiles. It knows why you love Katy Perry but hate Lady Gaga. It knows why you might want to hear a Jay-Z song on your Fiona Apple station. And once Pandora begins to collect and analyze data on how these political ads perform, it can identify even more unintuitive insights that are of great value to political campaigns. For example: Against all odds, maybe New Yorkers who listen to a combination of John Coltrane, Avicii, and Bob Marley lean Republican.

Advertising against music, which inspires passionate reactions, may also amplify a politician's or lobby's message. Say you're listening to Rage Against the Machine and Public Enemy -- That's the perfect moment for a political ad about police corruption.

The only data Pandora overtly collects from users are email addresses, birth years, genders, and zip codes. That's not so bad, I suppose. But the insights it can collect from the music we consume are potentially far more intrusive. On the political side, will the government flag me if I listen to musicians whose lyrics have extreme political underpinnings? What if I'm researching a piece on neo-Nazi rock music and how it's used as a "gateway drug" for young recruits? On the advertiser side, if I listen to a bunch of breakup songs will I hear ads for Match.com and Kleenex?

For opponents of what Yasha Levine calls Surveillance Valley, exchanging personal data for free services is hardly a fair trade. For my part, I'd rather pay Pandora $3.99 and avoid ad targeting altogether. But millions of users disagree, which is good news for the people selling you products and, starting next week, ideas and candidates.

[illustration by Brad Jonas for Pando]