One of the things that we love best about Reader is the ability to easily share interesting items with your friends. In fact, we like it so much that we've been adding bunches of new sharing features over the last year including choosing friends to share with, sharing with note and the sharing bookmarklet. But we quickly realized that one of the most important pieces of the sharing cycle was missing: the ability to have conversations with friends about all those shared items.
At this point, RSS feeds are more critical to my work as a writer than e-mail is. Being able to share items with friends, see their shared items, and comment back and forth is extremely valuable to me. No matter how busy I get, I always at least glance through my friends' shared items. There's no other feed I pay that much attention to. And there's no feed I get more valuable surprises out of.