> Ok, your proposal has the disadvantage that the error occurs only when
 > referring to the label (and at the point of reference instead of
 > definition).

so does yours i think, or how was your proposal meant?

 > And it has the advantage that if you are only out for a
 > \pageref in the first place, this will still be legal.

well, compare it to the outcome of your proposal which looks like this:

! Undefined control sequence.
\@currentlabel ...ing \label inside of a figure.

l.22 \label{foo}

i guess it is fairly difficult to find a short enough csname that in the above
output will look reasonable and b) it will still probably open more questions
than answering them

 > > any suggestion for a good text?
 > \label{whatever} without preceding or enclosing \caption.
 > Labels must follow the item they are referencing.

well "whatever" is not known when we generate that text, is it?