Of course there are always windows that are better off with little or no window treatment such as this example from BDG Style. Love her blog, by the way.
However, if you do have larger windows that call for curtains, I almost always recommend hanging the rod just under the crown moulding and to either side of the window so that the majority of the window (minus the casing) is exposed. This allows maximum natural light to enter the room and it just looks better.
Here are a few examples...
Ashley Whittaker via
Are you convinced?