Pretty interesting theory by Ku Dang about the latest change within google. It does seem partly true. He calls it the Google Kettle Theory. Read about it here:
http://seo-uk.newsvine.com/_news/200...-kettle-update
It does seem Google is playing with some filters and it is around links. Not sure about the age of links but perhaps more about link placements on a page. I have seen one of my pages go in and out of Google and all of the links are not in-context links but side bar type of links. Nothing conclusive - just an observation.