To be fair, at least at FB (I can't speak to Google or Apple or Amazon):
1. Accessing someone's data when it's not mission critical to your work means you're fired on the spot. This is drilled into new engineers over and over.
2. Privacy-related issues are escalated to the highest severity immediately (on par with data centers being down, etc.). I think the question in this whole debate is where you draw the line for this kind of issue, and what's an issue and what's a feature.