The New Social Bing in US

@adCenter Tweets 

Microsoft adCenter ‏ @adCenter Sneek peak of the new Bing Socially integrated homepage (currently in the US)! #SMX http://twitpic.com/9la9fq

from The Bing Team : Introducing the New Bing: Spend Less Time Searching, More Time Doing

Microsoft adCenter in Australia

From Microsoft adCenter

The ads you create in Microsoft adCenter can appear on a variety of Microsoft properties, such as Bing search results pages, relevant MSN-affiliated websites and Microsoft Office—to name a few. They may also appear on Microsoft partner sites like Facebook and the Wall Street Journal Digital Network. The placement and ranking of your online ads are determined by several factors, including search keywords entered by your customers and the type of content displayed on participating sites.

 Also from the adCenter Blog,  Introducing the New Microsoft Advertising adCenter Training Hub

But for now you can not run your ad for Australian market.