I was just on Facebook, happily commenting on various entries, read one by a colleague, a beautiful quote, and was going to comment.  Then, I noted that the person who commented first was a person who owes me money for advertising and refuses to even discuss it.   I stopped dead in my tracks, unable to make the posting.  Am I alone in being uncomfortable in being social with the debtor?  Should social networking be similar to going to a party when someone else attending is known to be a less than reputable player and you merely keep quiet and talk with the others?

How do you handle such situations?