I had more than only one broken card so far.
I blamed (intentional) excessive use for that by having lots of different applications run on it that all write blockchains (e.g. peercoin, emercoin, slimcoin, nu).
Maybe it was not only the intentional heavy use, but an unintentional one as well by those application creating more I/O on the SD card than expected.
The symptoms were different: not being able to login via SSH (I run the RaPi only in headless mode), commands that can’t be executed when logged in, etc.
The reason for the symptoms was always the same: a corrupt files system that couldn’t be fixed by fschk. And the reason for that corrupt file system became obvious after having dd’ed a backup image to the SD card: file system corrupt right after writing it; an SD card beyond its wear level capabilities.
I thought about switching from ext4 to another file system or disabling the journal. But as I play with the RaPi more for fun and to learn something (learning to compile stuff, efficiently operate such a headless device (shell scripting, tools), learn to use RPC of the running programs) I simply grabbed another SD card and started all over 
The only thing running on my RaPi that is not only for fun are the TLLP bots for liquidbits, nupond and nupool. They run on a dedicated RaPi which doesn’t suffer from broken SD cards each several weeks to few months. That was the lesson I learned after the last SD card crash.
