I personally think that a research paper should NOT be presented at two
  different conferences unless the presenter, at the second conference,
  makes it clear that this is being done and what (if anything) is new from
  the previous conference disclosure.  Even then, this procedure should be
  only sparingly used.
 
  There are many pre-conference methods of getting feedback.  I think the
  conference presentation should be the culmination of a significant
  research effort; in most cases, the project can be refined for
  publication after one conference.  This is the protocol, I believe, in
  most scientific domains.
 
  To warrant presentation at another conference, the new, revised paper
  should contain the heft of new ideas, methodology, analysis, etc. that
  would virtually characterize an original paper.
 
  I have attended conferences, including some of our own, where the
  research and analysis were far too unripe for useful presentation.  In
  fact, I regret that some/too many of mine suffered from that.  To allow
  people to make inveterate presentations of the same or essentially the
  same paper would discourage ripeness and reduce the quality of
  conferences.  If the conference is thought too small for the magnitude of
  the work expended, pick one that is better attended.  This will reduce
  proliferation, and should actually strengthen the good conferences.  We
  don't get to publish in an "easy" journal and then cast around for a
  better one (bigger audience in the same field).
 
  Our students cannot use term papers or examinations for more credit than
  in one course, at least not without first disclosing and asking
  permission.
 
  I guess I take a rather legalistic view of disclosure of research
  (perhaps along the same lines of inventions and other discoveries).  When
  we stand up at a conference, I think we are impliedly representing that
  what we have to say is original.  That is the purpose of conferences
  (instantaneous face-to-face exchange of genuine research currents to a
  committed peer group).  Dissemination to the greatest number of people
  is, to be sure, not the objective of this medium.  To use conferences
  only to repeat what used to be original (would there be ANY limits to the
  number of times a paper is presented?), can only drag down the quality of
  papers and conferences.
 
  In an era when standards are being attacked on all fronts, I would like
  to preserve research as original, current and rigorous when presented.
 
 
  Peter Bowal
  University of Calgary
  Alberta, Canada