Quick comment: True according to Shia prophets do not do Taqiyyah since prophets are the only source of religious knowledge in their times. Ironically, most Shia will quote verses about Ibrahim (as) doing Taqiyyah in the Qur'an to back-up their stance. Their Taqiyyah belief is refuted by highlighting the fact that according to them, the Imams were also the only source of religious knowledge in their times, in this sense no difference between Imams and prophets and thus the weak belief collapses.
I agree with you Hani. But I believe there are some circumstances where knowledge should not be revealed for either of two reasons:
01. Where the person (i.e. Imam or religious scholar) life is in danger.
Sahih Bukhari
Volume 1, Book 3, Number 121:
Narrated Abu Huraira:
I have memorized two kinds of knowledge from Allah's Apostle . I have propagated one of them to
you and if I propagated the second, then my pharynx (throat) would be cut (i.e. killed).
02. For the benefit of the questioner:
Sahih Bukhari
Volume 9, Book 88, Number 211:
Narrated Anas:
The people started asking the Prophet too many questions importunately. So one day he ascended
the pulpit and said, "You will not ask me any question but I will explain it to you." I looked right and
left, and behold, every man was covering his head with his garment and weeping. Then got up a
man who, whenever quarreling with somebody, used to be accused of not being the son of his father.
He said, "O Allah's Apostle! Who is my father?" The Prophet replied, "Your father is Hudhaifa." Then
'Umar got up and said, "We accept Allah as our Lord, Islam as our religion and Muhammad as our
Apostle and we seek refuge with Allah from the evil of afflictions." The Prophet said, " I have never
seen the good and bad like on this day. No doubt, Paradise and Hell was displayed in front of me till I
saw them in front of that wall," Qatada said: This Hadith used to be mentioned as an explanation of
this Verse:--
'O you who believe! Ask not questions about things which, if made plain to you, may
cause you trouble.' (5.101)