Let's head on over www.googlebooksettlement.com, shall we?

"If you do nothing, you will be bound by the Settlement. If you do not claim your Books, you will not receive any Cash Payment or be able to participate in future revenue from Google’s use of your Books. By staying in the Settlement, you will, however, release all copyright infringement claims you might have against Google for digitizing your Books without your permission."

This isn't adverse possession, where Google gets the rights after open and notorious use of ten to twenty years (depending on jurisdiction). Any adverse possession has to toll from the date of first infringement; according to Google's admission, that date is 2004. In this situation, a group which does not have title -- the Author's Guild, the Association of American Publishers, etc. -- selling the property on behalf of those who did not consent to these agents. We are told that this is mollified by "generously" allowing authors who do not consent to having their rights sold without their permission to opt out of this agreement.

(And since one can't opt out unless one is certain one has rights that Google is about to infringe or gets notice from Google, if Google can't find someone who didn't already know about the settlement, that someone don't get the option.)