This threads are turning more and more bizarre..., I haven't experienced this issue and I have a 2013 15" rMBP with a SandDisk SSD, I have copied lot of gigabits of information from a USB drive/Internet and the fans remained quite, my rMBPs fans ramp up very little for some minutes but I think not only the CPU generates heat inside but ALL components can do it and the machine needs to extract this heat in order to cool down everything inside. I think some people might be experiencing that their fans go crazy very often, but this is not my case and I think this issue is not generalised as some say.