Music recommendation service Pandora marked today what it calls perhaps its proudest milestone in 6 years since launching: 10 billion user interactions indicating approval or disapproval of a particular song. Those thumbs up or down are used to determine subsequent recommendations for a particular user's Pandora channels.

The 10 billionth thumb was pointed up and was for the song "Ridin' Solo" by Jason DeRulo, an autotuned song I personally consider annoying and repetitive. That's the beauty of Pandora: I don't have to listen to anything like that song if I don't want to.

Pandora faces far more competition today than it has at other times in its history, but as free, easy to use, lean-back music discovery experiences go - it's still very hard to beat. Unless you're not in the United States; in that case this whole conversation is likely a sore one.

None the less, the company and its capacity to turn user feedback into more intelligent recommendations have become a metaphor for many people. A Google search for the phrase "like Pandora for" returns almost 50,000 results, including links to things like a "Pandora for movies" (Jinni), a "Pandora for books" (many different sites) and "Pandora for bros" (fratmusic.com).

Above: A photo of Pandora's community manager Aaron Morgan, from Twitter.