because apparently they use elves to customize your Reader news item list by your karmic aura. Or something.

Official Google Reader Blog: Reading gets personal with Popular items and Personalized ranking

Personalized ranking – Only have a 10 minute coffee break and want to see the best items first? All feeds now have a new sort option called “magic” that re-orders items in the feed based on your personal usage, and overall activity in Reader, instead of default chronological order. Click “Sort by magic” under the “Feed settings” menu of your feed or folder to switch to personalized ranking. Unlike the old “auto” ranking, this new ranking is personalized for you, and gets better with time as we learn what you like best — the more you “like” and “share” stuff, the better your magic sort will be. Give it a try on a high-volume feed folder or All items and see for yourself!