As a person who doesn't log in unless presented with "tough beans" from spam filter, I disapprove of this measure.

The only other websites employing this tactic that I know of are social networks, designed to waste people's time and get them addicted, so the moment one tries to break the habit of checking the feed for more distracting shiny, they tug on the leash to try and make the user return, while the owner of the platform gets money from ads and personal data reselling. While PerlMonks is of course a much nicer place, I can imagine some backfire if we started sending e-mails to people who decided not to visit the website for their objective reasons.

At the very least, if implemented, this feature should have some means of turning it off in profile settings.