Just randomly clicking the new feature links at the bottom of my flickr collection brought me to something I should get around top doing- getting a backup. Hey, what if Yahoo falls into the ocean?
Englaze Archive will create a data DVD backup of your original flickr photos, the original uploaded sizes, and preserve titles and captions (not comments). It costs US$29.95 for the first 1000 photos and then $4 for each next set of 1000 (I am now at only 954).
I will likely order one pretty soon. Just in case.