Keyholes vs. Missing Features

I just thought of another reason why a missing feature doesn't "feel right" to
me as a keyhole.  Consider again the physical analogy of trying to see the
contents of a room through a keyhole.  The keyhole doesn't keep you from seeing
anything, it just keeps you from seeing everything at once.  A missing feature
is something you can't see at all, because the author of the software has
failed to provide it.  

I realize that this analogy breaks down somewhat with restricted domain
keyholes, but I still think that a missing feature is qualitatively different
from a keyhole.

Scott