From the Search Alliance Transition team:
Soon, you’ll need to either create a new adCenter account, or link an existing adCenter account to your Yahoo! Search Marketing account. Later this month, you’ll see an “adCenter” tab within your Yahoo! Search Marketing account. Clicking there will take you to the beginning of the account transition process, where we’ll walk you through the simple steps to create or link accounts.
I can’t wait…
I am sure the professionals at both Yahoo and Bing will be doing everything in their power to make sure the transition goes off without a hitch – I just hope the new Yahoo Bing Search Alliance doesn’t end up costing advertisers like myself more time and money.