I thought this would never happen to me, but it did.
The day before the wedding I ran to Fry's and got 2 RiDATA memory cards to increase by total capacity to 30GB. 4GB each, 233X, CF type. So last night after the wedding, I came home and started downloading form the cards. One was ok, but the other one was half ok. I used it on two bodies, the 30D files survived but the 5D files are not even there... and I got some of the best shots there, although it was towards the end of the wedding, I still will never go back to RiDATA cards ever ever ever again.