Two researchers of Hewlett Packard's Social Computing Lab, Sitaram Asur and Bernardo Huberman just published a paper in the HP site presenting the findings of a study aiming at measuring the predictive value of the Twitter chatter in particular for estimating the revenues of movie films. The paper is not submitted to any journal yet, at least as far as I could understand.
Listening-in the customer voice is something I recommended as a way to use the Social Media as Marketing tools in my first published paper about this issue back in 2008. This new study provides new evidence of the value of the Social Media as marketing tools and I think that more studies will follow. Next to the high quality results obtained (the researchers claim that the Twitter-based predictions outperform traditional prediction methods) such research has also another advantage versus the traditional ones. It is much cheaper, something very interesting for businesses and mainly the small ones.