Correction:
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Organizations fall over by default, slowly enough that you can fix them if you care.
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Ed did NOT say that because organization fall slowly it's hard to notice.
He implied that you have time to fix the failure... you just have to put conscious effort to notice the problem and then another effort to fix it (while organization is still successful overall).
He says "... organizations are inherently unstable, they will fall over, you have to work to keep them upright, but they fall slowly, most people don't notice it, they let success blind them." -- roughly minute 34.
I wouldn't want to misparaphrase him, but I think my notes are accurate.