But I'm reminded of the ancient Archimedes manuscript. A medieval monk needed some vellum to write his thoughts, and instead of going to get his own new vellum (here, little sheepy ...), he just erased the ink from an existing, but not very interesting text. Through modern multi-spectral scanning, scientist were able to recreate much of the ancient document. But that's the problem with USB drives - they are just to tempting to pull out and overwrite.
So I decided to use the trusty old DVD-R format. But if I want these photos of our family to last 100 years, beyond the coming economic Apocalypse, which disks to use? After more research I settled on the new JVC J-DMR-ISO-WPY25-HC. They are insanely expensive and only hold 4.7 Gig, but if you have documents to pass on to your great-grandchildren, a few more bucks to make sure the DVDs survives is worth it.
Note to grandchildren: In 2114, please try to read the "Sony 2014" backup disks and add a comment to this post if you can read the disk.