Google Reader added a way to see "personalized trends for your subscriptions and read items". You'll be able to see how many posts you read daily, what are your favorite feeds, the most prolific authors, the most inactive feeds. This is also a great way to decide if you actually read a certain feed or you just keep it in your subscription list because it's too difficult to unsubscribe.
{ Thank you, Jeff G. }
Update: Some people shared their stats: Matt Cutts, Mihai Parparita, and more.