I think it's pretty darn simple.
There should not be anything wrong with posting about a vendor that you had a problem with, the attempted to resolve the problem with the vendor directly before posting about it. For example the original post in this thread. Benjammin had an issue with classiccruiser.com. He then contacted classiccruiser.com to attempt to resolve the issue. He got a reply back from classiccruiser.com. He did all that before he posted anything. If the story is not complete (whether it is a satisfactory end or a frusterating one) then do not post anything about the situation. The original post in this thread is a good example of how to post about an issue with a vendor. It is a complete story.
This forum should never be used to resolve issues with vendors, period. That is what private messaging, email and telephones were made for.
Soren