CDs and DVDs can delaminate... they actually fall apart, making them useless. There may be other means of destruction as well, but you have to either be very careful, or assume you are going to lose SOME photos, or both.
I buy the more "expensive" archival-grade media, but that could well be snake-oil and I may get boned in the end anyway.
I can say that a friend of mine did his own test of the various kinds of media, subjecting them to these horrible and unimaginable torture tests... leaving them in the shower for a month, leaving them on the dashboard of his car through all of August, etc. It was pretty crazy. In the end, the stuff I have won hands-down. I believe the ones I have currently are the MAM-A. Back a few years back I was doing Kodak Gold, but they stopped being available for some reason.
My current plan is to every 6-7 years copy all of my existing archives off to much larger capacity "archive" media, and still keep the old stuff. I figure if I do this, odds are reasonable that I will minimize the loss over time.
Here's AN article on the topic... there are many.
http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media
And yes, this topic comes up a lot so do the search thing.
