Many pro photographers use CD/DVD as a third form of backup. It is the cheapest way to store images that may never see the light of day again. I use DVDs to archive year-old jobs, especially the images that didn't make the final edit. I do this because I'm confident I'll probably never need an image from that disc again. (It depends on the job, though.)
Archiving on external hard drives seems to be the most reliable trend. But I would read MacGurus.com and other places before I would trust LaCie with my "star" RAWs. It seems Hot-Swapable SATA Burlys may be the best pro choice for the future.