MusicBrainz is a free-to-use encyclopedia of music-related metadata (all that information, like artist name, track name, composer, etc.), and like a lot of free-to-use services, it has a commercial tier for companies whose use would put an undue burden on the service. Yesterday, the folks at MusicBrainz sent over a cake to Amazon to remind the online giant that it hasn’t paid a 3-year-old invoice for its commercial use of the service. Let’s hope the accounts payable people got the message before someone just left it in the break room for everyone to gorge on. [via Boing Boing] [More]