Yesterday was the limit until which former users of MobileMe could transfer their files from the old service to the new iCloud, their space limit to be reduced to 5 GB if they did not purchase more space. Although Apple had to reduce the space offered to them, it seems that an error of engineers offered 25 GB of free space to former MobileMe customers, the offer expires in 2050. Apart from former MobileMe customers, other users received this bonus from Apple and most of them have never used MobileMe.
It is not known if users can use the free 20GB for anything, but Apple will surely fix the problem today and all those who received extra space will quickly lose it. Some speculate that the free space would have been offered as an attempt to appease users upset by the uselessness of the Maps application, but I don't think it can be about such a thing.
