It depends on the context. My website gets responses from readers, which I can respond to privately, but I'll very often publish the comments if I think other readers may be interested. Since they were posted to a public website, and the user didn't ask that it be kept anonymous, I simply 'accepted' the commented and it was published on the website.
However, the SOL blog is separate, as there's no assumption of public exposure. That said, SOL is different since it's a 'private' website, requiring a password to gain access to the material, meaning a spambot can't simply pick up the email address by performing global searches. So it's a tricky situation.
Still, I wouldn't publish the user's email address, since the communication was private. In fact, I'd be reluctant to even use their SOL user name (though again, many responders use a separate email address, or at least I do). Still, that's an unnecessary exposure of a private communication, while the public website carries an expectation of public exposure.
However, I also list my own email address, though I'm careful where I display it. I list it as a contact on my website (probably a dangerous thing to do), but not on public websites like LinkedIn or even on the SOL Forum. I also list it in my books as a way for readers to get in contact with me, but again, it's not generally accessible via search engines as you'd have to purchase the book to access it.
Aerosick, if I was you, I'd send the author a private note, pointing out the abuse of private information. S/he was probably unaware of their blunder, likely never even considering it. That provides a way for them to rectify the situation.