Narkissos: A question booker-t might ask: suppose the WT is wrong on, say, 1914. Suppose a JW comes to disagree with the current WT stance on 1914. What will happen to him/her? So what lessons have been learnt from past mistakes?
Excellent point!
In the case of Peter, did he disfellowhip any who disagreed publicly with his view? Did he claim that it was Jehovah's Word spoken through him as the Channel of Communication (capitalized as an official title and everything)? What about Jonah? Did Nathan cast people off from their family and friends for not believing that David was going to build the temple?
The impacts of the thing spoken in the case of Witnesses is that it becomes indisputable doctrine, part of "the pattern of heathful teaching" and part of "the truth." Until it changes, publicly arguing against it or challenging it for Biblical grounds will get you disfellowhipped so fast you'll get whiplash.
Respectfully,
OldSoul