These two quotes provide an interesting framing for comparing and contrasting the UI and functionality for the way that feed readers, email, and blogging (or more broadly networked thinking and communication) work.
Modern social readers provide a reply button and functionality along with the broadcast capabilities. Throw in the idea of person-tagging, and one has the ability to generally broadcast a message to anyone who cares to read (either by search or subscription), as well as to send notifications to specific people (or perhaps groups) that might be interested in the specific message.