Just to clear up a couple of points. If you don't get your socks right when you play tennis or run, you are likely to end up with blisters; especially if you perspire a lot; anybody who spends more time on their feet than on their arse will tell you that you have to look after your feet. If I got out any more, I'd never be in and 'socks with sandals' go and wash your mouths out !
If you haven't tried it, don't knock it ; it is much easier to get your feet into flat socks. I was gratified to see so many replies to this bit of trivia; thank you all.