Perhaps Google has added P3P to the many factors in their algorithm, as they have done with the age of the domain name (See
The Age of a Domain Name on
webconfs.com).
It appears that they want to have some way to ascertain the reliability or trustworthiness of a page. Obviously, this is a very difficult thing to do with a computer algorithm, no matter how complicated. I guess the P3P information may be another of Google's indicators.