SFGate reports that YouTube develops a technology that "will allow copyright owners to identify their content, locate it and then make a decision based on whether they want to remove it. (...) The new technology will be designed to scan a digital audio file, such as an MP3 or video, and compare the electronic fingerprints to databases of copyright material."
YouTube has deals with Warner Music Group, Vivendi's Universal Music Group and Sony BMG Music Entertainment that involve ad revenue sharing, so the content providers need to detect their content. To be successful, YouTube has to make deals with all major labels and develop a flawless detection technology. Google is going to be helpful, it will bring more credibility and a better technology (Google acquired Neven Vision).
And if this works for videos, it should work for music too, so this might be the seed of a legal file-sharing site. Unlike other solutions like Mashboxx, the content will be ad-supported and only available online.