I read in the Diario Vasco newspaper (online article[es]), that Microsoft has been recently sued by Alcatel-Lucent over some MP3 patent infringement, and found liable for a fine of around 1.100M euro. MS alleges that they did pay the Fraunhofer Society $16M for these very rights.
All this rubbish is typical of Microsoft and their obsolete proprietary model. They are the dinosaurs of the XXI century. MS could include Ogg Vorbis support in their music player(s), and forget about patent issues, since Ogg Vorbis is open and free. However, all the friends I have that use MS Windows complain if I share music in Vorbis format with them, and I am forced to convert it to MP3 (actually MP2 Layer 2, not Layer 3, which is the patented one) if I want them to listen to it.
The choice of MP3 is an unfortunate one, because it traps MS in a legal nightmare of patents and licenses, yet they'd rather face it than switch to something that "stinks" of freedom. One more example of the absurd ways of the Redmond smartasses.