One should not crop more than needed,
One should compose correctly instead of using post processing,
But....
I'm loving all those pixels in the D800. This image is 2.2% of the full frame.
Just in case you think that's a typo, it is 1/45th of the frame. It's the head of a burrowing owl in Cape Coral Florida, taken today in light drizzle (you can see the feathers are a bit wet), NIkon 200-400 @ f4 @ 400, ISO220, 1/250th.
It wouldn't hold up to a large or even medium sized print. BUt it is rather nice when one doesn't compose fully in the frame to have enough pixels to get a tight crop.