  A precise definition of "weak [quantum] measurements" and "weak value" (of a
quantum observable) is offered, and simple finite dimensional examples are
given showing that weak values are not unique and therefore probably do not
correspond to any physical attribute of the system being "weakly" measured,
contrary to impressions given by most of the literature on weak measurements.
  A possible mathematical error in the seminal paper introducing "weak values"
is explicitly identified. A mathematically rigorous argument obtains results
similar to, and more general than, the main result of that paper and concludes
that even in the infinite-dimensional context of that paper, weak values are
not unique. This implies that the "usual" formula for weak values is not
universal, but can apply only to specific physical situations.
  The paper is written in a more pedagogical and informal style than is usual
in the research literature in the hope that it might serve as an introduction
to weak values.
