[BeetleB]

Think of it as "if they respond to the challenge email it'll get in front of my eyes quicker".

Also, keep in mind when I wrote it, I was getting 20-50 spam a day (not counting unsubscribe emails). And part of the motivation was that legitimate emails were simply getting lost (I wouldn't notice them in the sea of noise). Checking once a week would mean scanning hundreds of emails for the few legitimate ones. The challenge-response is more reliable.

(Today I get almost no spam - someone fixed a broken pipe on the Internet).