Thieves get rich, and saints get shot, and God don't answer prayers a lot. And free online music-streaming services may not be as benevolent as you thought. Thanks for that, Spotify.

Spotify currently supports its free music-streaming service with adverts - every 10 songs or so, you hear an audio advert, and there are also less intrusive visual adverts. Most people don't have a problem with the ads, figuring that it's a small price worth paying for free music. Spotify's popularity is exploding.

But we now know, thanks to a revealing interview that you can watch at the Guardian's website, that Spotify is planning to increase the creepiness factor, if you will, of its advertising model. It's exploiting the demographic information it has on each user, together with playlist information, to 'serve' adverts that suit that person's age, gender and even mood.

How to use Spotify

Listening to Mozart and knocking on a bit in years? Perhaps you'd like to hear about our range of life-insurance options while you're nicely relaxed. Young, male and giving the Wu-Tang Clan a few spins? Anger management courses if you please.

Nick Drake aficionados, meanwhile, could have a public service announcement every 10 songs advising them to cheer up and not take life so seriously.

Well, we're sure they'll work out the details.

Thing with this is that people are funny about having the details of their personal habits flogged to advertisers. Look at the hoo-ha surrounding the Phorm targeted-advertising system, which helps to serve ads based on victims' browsing habits. There's a feeling that this sort of thing betrays the trust users have in a service, selling them down the river for a quick buck.

One way of looking at this is that, if anything, it'll mean that you get adverts for products you might actually like, which ought to be less boring. Another is that it's no one else's damn business what music I listen to; yet another would be that there's something truly hateful about advertisers profiting from the emotions brought about by cherished records.

Music is supposed to be spontaneous, to surprise, excite and move you, not put you in a mood to consume products. Just imagine some advertising flunky rubbing their opportunistic hands together when they look at your favourite upbeat playlist. (Yes, I know that's not how it works.)

Ultimately, however, we get the music industry we deserve. Significant segments of the music-consuming public have decided that it ought to be free, but without thinking through the consequences of that. It's a zero-sum game: the money required to produce music has to come from somewhere. If none of us are paying for the music directly, the advertising has to be effective, and we're all getting too canny for the normal stuff to be cost-effective. Which is why we now seem to be living in the Orwellian action thriller Minority Report. "Your futuristic ID chip tells us you like to buy Gap V-necks, Mr Cruise. The child sizes are over there."

Talking about Phorm, Tim Berners-Lee has insisted that his data and web history belong to him. "It's mine - you can't have it," he said. "If you want to use it for something, then you have to negotiate with me."

Spotify provides free music in return for listening to adverts, but its targeted ad system changes the deal. Maybe its time to renegotiate. Unfortunately the only way for us to do that is to stop listening - and what are the chances of that?