Developed by an Iowan teenager named David Nelson, Muziic is a desktop application (and, as of this March, an iPhone and also a Facebook app) that scours YouTube for song streams which people can basically use like MP3s: users enter song titles or artist names into a search engine, and the results of those searches can be compiled into playlists, cached, and stored for offline use, just like a user can do with subscription services like Spotify, Rhapsody, MOG, or Thumbplay.
The only difference is that Muziic is free, and it also doesn't pay licensing or royalty fees to artists. Neither YouTube nor any of the major music rights-holders has attempted to sue Nelson for some reason (possibly because YouTube, as the host of this content, is already rendering fees to the artists).
According to TechCrunch, Nelson and Muziic are discussing" licensing options with various labels, and you can bet those labels are praying like hell that those discussions get somewhere. With industry people privately fretting about Spotify and Pandora to lure users out of their free tiers and into paid ones, Muziic is clearly capable of submarining those initiatives, possibly permanently.