A few days ago I bought this off ebay: http://www.ebay.com/itm/171748969707

I had planned to use this card with a Raspberry Pi 2 but, after flashing, it would not boot. After writing 56 one-GB files to the card, the linux F3 program stopped and I couldn't open the sdxc card anymore. After reformatting I started copying 1-gb files on by hand. I found that only the first eight survived - after that, comparison with the originals showed they were corrupt. Also, the speed was only 5.8 MB/s.