That's very interesting but in the OP he couldn't tell anyone, which makes me wonder how many people would need access to stop the canary message being sent. I

That's very interesting but in the OP he couldn't tell anyone, which makes me wonder how many people would need access to stop the canary message being sent. I can imagine NSL-like letters being sent directly to individuals to coerce/threaten them into handing over data, without the management/legal team ever knowing. Of course, having such a canary message is likely better than not having it.