Why do so many players wimp out against Federer?

Part of the problem is the "intimidation" factor of Federer. Many players are already beaten in their heads when they know they have to play him. It happens with a lot of number 1 players, their opponents think they can't be beaten so their game falls away. Tennis after all is largely played in the head if all the usual shots are there and you are very talented - what's left is what goes on between the ears!