The supposed open forehand stances of the modern game
If you read tips online, then you will often find the tip "Open your stance up" (c.f. closed stance).
While a more open stance is certainly preferable over full closed, I've actually noticed that few top players utilize a full open stance.
Federer, Agassi, Moya, Safin, and Roddick all use "square", or 3/4 open, stances to hit their forehands.
Does anybody else notice this?