This is the first thread I have seen on the topic of the old 1 cent bids from back in the GoTo or Overture days are no longer going to be in affect with the new Yahoo! Search Marketing Panama release. A WebmasterWorld thread quotes an email an advertiser received that states;
Important Note Regarding Grandfathered Bids : In addition, our current minimum bid requirement of $0.10 will be enforced after an account is upgraded. This will impact your keywords that are grandfathered to bids below $0.10.
This particular advertiser has 2,000 plus keywords set at one cent per click.
If you are one of those advertisers, make sure to carefully watch your budget as you upgrade over to the new system.
Forum discussion at WebmasterWorld.