Got this from from Google Adwords in my email:
Preferred Cost Bidding is being retired as a bidding option for all AdWords campaigns as of January 26, 2009. This change will take place in two stages:
(1) As of right now, preferred cost bidding still works in existing campaigns where it has already been selected. But it is no longer an available option when advertisers switch bidding types or create a new campaign.
(2) On January 26th, preferred cost bidding will disappear completely. You should switch all your existing preferred cost bidding campaigns to other bidding formats before that date. Continue reading