You probably forget the things you don't need, and forget that you actually knew them. It's not a first-in-first-out, but governed by use counts. Use it a lot, keep it. Don't use it much, forget it - room for the next thing.
So, what is your definition of "The Cloud"? I have seen several kinds of things refered to as the cloud. Things like other people's storage like Dropbox or flickr. Things like other people's cycles like Google Docs. Things like that vertical market application you run in a web browser (like the ticket tracking software where I work).
I wonder if the specific parameters used to identify a card (note not a user or a machine...) can change as the card ages, as it wears. Heat/Cold cycles, failing bits in memory, changes / updates in drives, malware infecting drivers or firmware... (that last would be -real- fun... suddenly you are not you.)