ed, JF made the statement in a conference call in 2006, that he expected to only use 9 billion, but authorized 25 billion because 25 would be the most he could conceive of using ("expected" being the operative word. Easy to get around that one).
He went on to state that the 25 B number was so that if the 9 B wasn't enough, he wouldn't have to increase the shares authorized again. Or something to that effect. It has been awhile.
I think it was in a summer (maybe May/June) conference call.