Yesterday The Verge revealed that Google “made it really easy for strangers to email you”. Google being Google. No one can out-Google Google.
Anyway, TUAW shows how to turn it off.
To respond on your own website, enter the URL of your response which should contain a link to this post's permalink URL. Your response will then appear (possibly after moderation) on this page. Want to update or remove your response? Update or delete your post and re-enter your post's URL again. (Learn More)