Outrageous sock yarn failure!
My daughter knit these socks from "Knitpicks Essential" yarn (now renamed "Stroll Sock Yarn"). She has only worn them a few times. Each time she has worn them they have formed huge pilling masses like this within a few hours. By the end of the day she can pull an entire wad of loose fibre from the bottom of her sock.
What a heartbreaking failure! They were nice socks.