Tarek,
Correct. You are not allowed to discuss specific questions that you encounter on the exam. However, you are allowed to say things like: "It was good that I had studied Earned Value formulas and how to manage virtual teams for my PMP exam." And I can ask things like "If you had to do it again, what topics would you study more?". This is completely ethical, because we are focusing on the How and What to study for the exam.
But more importantly: PMI has published the PMP Exam Content Outline. In this outline they clearly define what a person has to know in order to pass the exam. The concepts are right there described for you. This document is about 15 pages long and it is the perfect basis from which to create sample questions.
This is in fact the approach that we took for
www.pm-exam-simulator.com
. We analyzed the content outline and ensured that we have questions for every concept that is mentioned in this document.