I (and all Punchfork users, I assume) received a notification on January 3rd, including the following:

    Initially, support for Punchfork will continue, but
    we will soon be retiring the Punchfork site, API and
    mobile apps. We believe that a unified destination
    benefits our users in the long run, and the Punchfork
    team (me) will focus on contributing to Pinterest as
    the premier platform for discovering and sharing new
    recipes and other interests on the web.

EDIT: Gmail binned this email in "Promotions"... I wonder if that explains why some didn't see it?

I'm also a registered user and didn't get the notification.