I have to add to what Alan wrote that we first expect members to attempt to resolve issues all by themselves.
This includes sending pm´s, emails, and if the other party does not respond it´s time to start a paypal claim.
If all of this fails, then contact a member of the staff. We then will try to mediate in the issue. In the meantime it´s okay to post a (still) respectful "Where is my item"-question in the original sales thread.
The reason is that we primarily give everyone the benefit of the doubt, life can get in the way of the hobby. But we have a very low tolerance threshold, meaning that we will take measurements against a member that does not deliver an item if we do not receive a reaction within an acceptable time frame.
Starting a call-out thread should be done in a respectful manner, e.g. asking if anyone has seen member XYZ in the last few days or has contact with them, before throwing out probably incorrect accusations.
So, before starting a "call out"-thread it is never wrong to notify the staff.