Let it go or balk?

[Matthew F]

I'm a little confused also...

I've have been told it's a balk to throw to an unoccupied base. I've also been told that a pick-off throw to the F3, while not holding the runner and making no attempt towards the bag (i.e. F3 is 10'-15' behind the bag, catches the throw and just stands there), that it would be a balk also.

So why wouldn't throwing to an outfielder or infielder playing shallow outfield not be a balk?

EDIT
(got the part about throwing in the vicinity of 2B, but come on... a rainbow to the outfield?!?)