I had planned to use FILE VAULT as soon as I got my new MBA - before I started adding programs and data to it. Anyways, i got sidetracked and as is - my new MBA is backing up to a Time Capsule without encryption. About 40gb worth of system/data files. If i NOW enable file vault - I am guessing that the Time Machine will backup an entirely new 40gb worth of data to the Time Capsule - but can anyone confirm this? From what I know FILE VAULT creates an 'encrypted container' around your user and system files?