As I see it, crop is in relation to the standard of the mount.
We should just move past "FF" and "crop formats." That is, if we were ever really there. Try to find any company or reputable source that refers to a "crop format" or "crop camera" (that was the term that started this debate) and you will not find it.
The F-mount, or the EOS mount, or the A-mount are all 135 format mounts.
Mounts are not formats. You can use different formats with the same mount; and there are even adapters to mount lenses from a different format to a smaller format, so you can use a 135 format DSLR as a cropped camera too. Also, imagine if Nikon had created a new mount for DX format [this isn't merely hypothetical, see the last paragraph below], then your reason for referring to DX as a crop format should not exist in the first place.
This is also true for lenses. Thus, anything less than 135 are crops of said mounts.
It would be fair to say that the 135 format lenses are cropped, but that isn't a necessary condition of DX format as there are DX lenses; and lenses, mounts, and formats are all separate aspects of the camera.
The same is true for MFDBs, the standard for mounts and lenses is 6x4.5+, thus the cheaper MFDBs like the Pentax 645D are crops of the format.
I believe the Pentax 645D is a DSLR. Anyway, can you direct me to anyone calling the 645D or MFDBs "cropped cameras?"
Full frame cameras use the whole frame the mount is intended to.
That is one rationalization. However, historically full frame has meant you use the entire format rather than for instance just half of it (which is half frame).
But no-one says that a D3x is a crop Phase One P 65+, or that the P65+ is a crop 4x5".
No one says that because they are different formats, just as DX/APS-C are a different formats from FX/135.
All are full-frame cameras.
All cameras are full frame until you crop them. I take full frame shots with my D300 all the time.
My point is that this is torturing the language, and that it is basically agenda driven. Designating some cameras as "FF" as if that automatically makes them better (and it doesn't) has lead to the inverse of that, and I would say that about 90% of the time when I hear someone referring to a "crop camera" or "crop format" it is meant to be disparaging.
You rarely see m43/43 referred to as crop-cameras, and more often as, well, m43/43 cameras. There are no full-frame cameras or lenses for that mount. Some, like Pentax, are still called crop-cameras, even though they don't make any full-frame gear. But as they're so similar to other APS-C cameras, and the K-mount is a 135 mount, it's still understandable.
NEX cameras have an E mount. They use the same sized sensor as DX cameras use. There will be no larger sensors used on those cameras. The same thing is likely to happen with Nikon when they introduce a mirrorless camera. So we will have two cameras using the same sensor (Sony already has this) and by your definition one will be "FF" and the other will be "crop format" or a "crop camera" -- as far as I'm concerned, that doesn't make sense.