On Wed, 12 Jan 2011 13:35:10 -0500 (EST)
Len Brown [off-list ref] wrote:

Do I care about the phantom configs that would be possible
if these false dependencies were not in place.  No,
not until somebody invents such a system,
and may be not even then.

Is there a user out there on LKML who can dream up
a use for one of these phantom configs and claim that
his life will end if he'd prevented from building it?
Sure.  Does he suffer from a total lack of perspective?
Yes.

These unusable config combinations should be prevented via Kconfig. 
That prevents users from selecting them, which otherwise adds to
our workload and to theirs.  It also prevents false-positives
during our useful randconfig testing.