When Apple replaced its MobileMe service with iCloud last year, it gave users of MobileMe, who had purchased extra storage on MobileMe the same storage on iCloud for an extra year.
I was a previous mobile me user, and when iCloud was released I was given an extra 20GB of storage on iCloud, this was due to run out at the end of September, but Apple sent out emails on the weekend to say that the extra storage had been extended, you can see the email I received below.
When you moved your MobileMe account to iCloud, we provided you with a complimentary storage upgrade beyond the standard 5GB that comes with an iCloud account to help you with the transition. Originally, this storage upgrade was set to expire on September 30, 2012.
As a thank you to our former MobileMe members, we will continue to provide you with this complimentary storage upgrade at no charge, for an additional year, until September 30, 2013. No action is required on your part. For complete details, please read this article.
Thank you again for using iCloud,
So basically, anyone who was allowed to transfer their extra storage from MobileMe to iCloud, will now get the same amount of storage for another year, this is on top of the free 5GB of storage that comes with iCloud.