Prologue:
I never ever had a major problem and disagreement with the game up until now and the horrible legendary implementation.
Some minor problems were that the game was extremely easy, therefore boring, in WOTLK before the Ulduar patch.
Other minor problem was that we waited for so long, before a few expansion were released, with nothing meaningful to do. That problem also happened in WoD where the extended wait of Legion expansion was annoying, but turned out to be a worth the wait situation for a great expansion. Perhaps the best, besides the legendary problem.
Finally other minor problems were some class balance issues, especially pointed against rogues and mages in Cataclysm.
Discussion:
What I want to discsuss, and mostly ask, is what do you think or remember where the situations, when the community kinda of strongly opposed a Blizzard decisions or lack of action. Was it LFR? Was it flying or no flying? Was it bots? What else? When did Blizzard actually made mistakes, and the community protested about them? And perhaps rank those moments from the most significant protest to the least.