I know people make mistakes and overlook things, but really...there is no excuse for this. I get about 8 emails from my registrars warning me before a domain expires...60 days, 45 days, 30 days, 1 week, then one like every day until the date. Unless these emails are going to an address nobody is monitoring I can't see how this can get overlooked.
If an email was sent to a mailbox that wasn't being checked, it doesn't matter how many emails were sent. I don't know if it's the case, just guessing as one possibility.
That's exactly true. Emails bounce and the person who is in charge of the domain often changes jobs and the contact isn't changed. Some go straight to the spam bin.
But you'd be surprised at how many people ignore even postal notices that some registrars send.
What you have to keep in mind is that restoring domains that have expired is a profit center for registrars. [1]
And having incorrect email contact info helps as well since not only does it favor that profit center but it also prevents competitors from soliciting your accounts (as well as preventing spam, right?)
[1] In the case of the nodejs.org domain it was taken offline on the day of expiration. It wasn't deleted it didn't go into redemption. Generally most registrars give some grace period (but if you aren't getting the emails that doesn't really matter, does it?)
There is a new policy being floated by ICANN that addresses these issues. If I can find the link I will post.
