Google has come under fire from content owners in the past over copyright infringement on YouTube, but it’s not afraid to take the fight to others. TorrentFreak reports that Google is threatening legal action against YouTube-MP3, a service that allows users to plug in a YouTube URL and convert the resulting audio to a downloadable MP3. Naturally, Google aren’t too happy about the service, saying it violates the Terms of Service for YouTube’s API. The website apparently rakes in around 1.3 million users per day, so you can imagine the sheer amount of material converted from YouTube’s servers.