"The data was deleted by a maintenance process that was inadvertently run against the production ELB state data. This process was run by one of a very small number of developers who have access to this production environment."
Most companies would have said "the outage was caused by a system being accidentally misconfigured" or even less; Amazon, in contrast, admitted (a) that a specific person was identified who made the mistake, (b) that he had access to the systems in question because a process was being run manually which should have been automated, and (c) that if there hadn't been an error in the access control rules, he wouldn't have been able to make that mistake.
I often wish that Amazon was more open about their internal systems; post-mortems are the one time when I'm never wondering what they're not telling me.