Weeeelll, I could ask one of the nine million 
lawyers I know but just offhand I would say that 
it wouldn't be slander OR defamation of 
character if you merely state that it is a list 
of people who haven't followed through on THEIR 
end of the bargain.  Stuff like that is usually 
a matter of public record anyway.  Newspapers 
even print recent bankruptcies/contract 
breachings.  Now if you put out a list that said 
that the people were evil assholes who 
frequently slept with their mothers and raped 
puppies-THAT would be slander and defamation of 
character.  As long as you have proof to back up 
your claims it's nice and legal.  God bless the 
first amendment.