Found something a bit annoying, I'm sure it is a "feature" but ...
Twice now at two different shoots I ended up in Bracket mode unexpectedly, found by noticing the it stop in the middle of a burst.
Once additionally on the D800 I ended up in TIF mode instead of RAW.
I think I've found the culprit, it's obvious and apologies if so obvious it need not be mentioned. And to those who don't chimp at all stop reading now.
The Bracket button on the D4, and the QUAL button on the D800, are active while in image display mode. And if like me, you use the thumbwheel to move through images... All it takes is a touch of the hand or finger on that button and you suddenly end up in bracket mode.
A lot of functions take you out of display (e.g. any touch of the shutter or AF on, or menu), but this doesn't -- you can happily change these settings while the image display is up. So if you brush against the Bracket button while scrolling images, you might just end up in 5 shot bracket mode without realizing anything amiss, just think it didn't scroll on one click.
FWIW in case anyone else mysteriously finds they can only shoot in bursts of 3, 5 or 7.