tedster - 5:10 am on May 31, 2011 (gmt 0)
We don't normally link to this kind of unsupported information, but it's a new direction and worth throwing into the soup pot. I actually am not boggled - it makes a kind of sense to me. I'm always after my clients to maintain clean mail lists, and I've long thought it could find its way into ranking calculations some day.
However, it's important to note that this report is about a MANUAL penalty being lifted, not about an automated algorithm factor.