[EM] IRV - disincentives

[Eric Gorr]

How would others answer this question:

   Is there a disincentive in IRV to rank candidates
   you do not want to see win?

I am thinking the answer is NO, but there is something nagging at me 
which says the answer could be YES.

Consider a case with four candidates and a voter who casts a ballot:

    a > b > c > d

but does not want to see either C or D win the election. It does not 
seem to me that the voter would be any better off if they had cast a 
ballot:

    a > b

preventing the possibility of their ballot being used to increase the 
vote total for C.

Which is then where the disincentive might come into play...the lower 
the vote total for a Candidate, the less of a mandate that candidate 
might believe they have...but is this enough of a reason to answer 
'YES' to the question above?