Too many skeletons in the closet. A subtly toxic culture, with pockets of good culture. An informed minority eats an uninformed majority and you might be left naively uninformed.
Things can fluctuate from feeling intensely watched, or being blessed with a miraculous amount of trust, and you may never know the difference. This can change at a minutes notice, and will feel powerless to navigate it. Some people who may struggle receive endless benevolent help and resources, and even limelight. Others are left in the dust.
Company culture is confused: you could potentially be afraid to speak truthfully, or tempted to follow everything BT with a cult like zeal, or you might never be satisfied with company progress in various frontiers. There is no way to know which of these options makes you stick out like a sore thumb either.
Layer cake of management levels with a huge legacy partition of employees. An application and infrastructure where depending on where you are assigned it is either a massive gridlock with a million guard rails, or greenfield projects with zero rules. Decisions here are behind closed doors and not systematic at all, nor seem fair. Advancement tracks for employees are the same.