Ubuntu can't play MP3s out of the box so how will we play purchased songs?
Canonical has put effort into making the customer experience as effortless as possible. When you visit the Ubuntu One Music Store, it will detect if you have MP3 support installed. If you don't, the store will install the Fluendo MP3 plugin for GStreamer. The MP3 plugin is distributed worldwide at no charge under a license from Fluendo. An Internet connection is required.