Thought this might be a good read. Incredible behaviour from what I thought were respectable companies. I've never had a Kingston USB drive or SD card go sour on me but I don't think I can support them if they pull stuff like this.

http://www.extremetech.com/extreme/1...r-good-reviews

The short; they switched to different/cheaper NAND/controllers after good reviews have been written about the drives with notable performance differences to the initial reviews.