I had a 2GB Datawrite CF card that was DOA four years ago. Other than that I have never had a card go bad on me in almost ten years of using memory cards. Nowadays I use 2 X Transcend 32GB 133X CF cards, which I've had for around 18 months, and used in four different cameras, all without incident. I also have Sandisk 8GB Extreme III 30 MB/s and some Transcend Class 6 SDHC cards (16GB and 8GB). Not a peep from any of them. Video, tick; 10 FPS and a big dump from my 1D3, 7D or 5D2, tick; no issues.
When 512MB were all the rage everyone cautioned against 1GB cards. This has repeated itself with every iteration of increased capacity, with doom mongers predicting the end of the world every time a larger card is released. Well 18 months ago I thought "b****r that!" and just bit the bullet and went for 32GB cards. I have no regrets. I probably wouldn't go larger than that because I simply have no need, but I certainly wouldn't fanny about with 4GB cards any more, not with a 7D and 5D2 churning out GB upon GB of raw files.