Ah, the joys of the automatic reply. Zagat canceled my subscription as per my request, and here’s what their e-mail included:

If you have a moment, could you let us know why you decided to cancel?
Is there anything we can do to change your mind? We rely on customer
feedback to make improvements to the site and the overall customer
experience, so we’d truly appreciate any comments you might have.

Gosh, I am SO glad I took the time to share my views in that previous e-mail.