[grahn]

The point I was making by comparing to a pilot, which I realise I could have expressed a lot more clearly, is that it is perfectly possible to mitigate risks through proper training and procedures even if it's not possible technically. (I.e. all it takes for a plane to crash is to turn the flight controls a few centimetres in the wrong way at the wrong time, yet it almost never happens.)

Of course things fail and people screw up. What I don't agree with are arguments along the lines of this just being a slight oversight, and that those can easily happen. It should require serious failure on multiple levels for anything like this to happen at that scale, if they are implementing things properly, not minor oversight.

[wrs]

Exactly — my scenario was an example of how failures at multiple levels could have caused this to happen. My "not-unlikely" is meant retroactively — now that it's happened, what's a not-unlikely explanation for how it was allowed to happen in a company the size of Facebook?

I didn't intend to imply it was a "slight oversight" — it's clearly a significant oversight — but there are people saying it's obviously gross negligence because how could this ever happen in a company that wasn't completely incompetent, etc. No, terrible accidents can and do happen even in companies that are trying hard to do a good job. Just like when a 737 crashes, you shouldn't assume Boeing is totally incompetent, but rather that several things must have gone wrong at once.