http://www.techi.com/2010/09/why-gmails-priority-inbox-needs-to-get-off-the-web-and-why-its-the-future/

The introduction of Google’s Priority Inbox in GMail was hailed by many as a step forward for email. Here finally was a way to not simply filter email in to spam and regular email, but a way to filter on what you read and replied to most.