Earlier quoted context omitted.
"I appreciate a good hack, but just can't get past the idea that this is a solution in search of a problem." I had exactly the same reaction: good hack, where's the problem? The solution to the problem of too much email already exists, and that solution is ... email. Email is asynchronous, and you get to decide when and what to do with it.
Overflowing inboxes are the problem. Perhaps we should have provided more context about what we're trying to fix : ) These guys do a good job: http://emailcharter.org We're trying to provide a framework around that first rule of respecting the recipient's time.
It's about sending only important e-mails/"not spamming". So, regardless of whether the guy I'm sending to has an empty or an overloaded inbox, I should always send the e-mail, because it's important.