Time for backupify.com?
i've seen some flickr-specific backup scripts that just dump all of the images to a directory, but they don't preserve titles, dates, sets, collections, tags, etc.
Why?
The difference between backing up your Flickr data to an encrypted drive at, say, Amazon and backing it up to an encrypted drive under your bed is: Amazon has better physical security, and far better redundancy, because (assuming you use S3) the "drive" you save it on there is actually a replicated data store that spans multiple regions and datacenters.
The point of backups is to provide redundant storage that is relatively uncorrelated to the original. Once you move the data to different disks at a different company in (if you like) a different country, you've done a lot to solve that problem.
also, many of the reasons backupify.com cites for needing backups would also apply to their own s3-backed service. "hackers", storage failure, human error, TOS violations, accidental account lapse/termination, etc.