Jim N, who does forensic legal work, writes with a great example of where a D4 makes sense for task-specific reasons:
I read a recent analysis of the D4 v. D800 with interest (mostly your site). I agree with essentially everything that was said.
I have sold my D3 and currently use a D4 as my "work" camera. Here are some of the reasons I use a D4:
1. 16MP files are plenty big. Often I shoot fine JPEGs, along with selected RAW (see below). 36MP files are overkill most of the time.
2. I need to describe many of the photos when I take them. Recording a WAV file that is linked to the photo saves a lot of note taking and is more accurate.
3. The easy transition to video and then back to stills. Video is why I replaced the D3 with a D4.
4. Nikon left out the ability to assign a function button (e.g. the Fn button) to the Shooting Menu Bank (the option is: SHOOT) for all cameras except the D4. I need to quickly switch shooting banks. (e.g. Bank A shoots RAW, Bank B shoots JPEG to a different card, Bank C is optimized for video)
5. The two toggle switches are very convenient when properly programed.
6. I have looked through the viewfinders of both cameras: The D4 is much better.
7. Although I am not an action photographer, taking a burst of several handheld macro shots usually means that one of the shots will be usable.
8. For some reason, that is not obvious to me, the D4 focusing system results in a higher percentage of in-focus photos.
DIGLLOYD: The D4 does offer some distinguishing features that professionals might find valuable (and others might not). I also like the build quality of Nikon’s pro bodies, and I wish the D800E sensor would appear in a D4x body.