OK, so the logic is this: 'normal' tube socks force our toes to work together, creating heat and moisture during exercise and creating friction.  Injinji socks, like gloves v mittens, allow the toes to work independently, and increase air and blood circulation.  Like most runners, we were sceptical at first, but soon found that having what Injinji call "individual compartments for your toes" really does work.  Injinji FAQ are here...