I got the same email from them yesterday, though it wasn’t as surprising as the email I received from them just over 1 year ago:
The Centrebet business has recently been taken over by Sportingbet and this agreement will come into force 1st January 2012.
As a result the Centrebet Affiliate Program will close its door on the 31st December to all Affiliates promoting to regions outside of Australia.
So the recent termination is not surprising for anyone not focused on the Australian market.