Ok, but from an economic perspective - if Topix is not collecting email addresses, how can they monetize all these people in the long run? From a marketing & user retention standpoint isn't that throwing away a pretty valuable channel? What monetary gain does 780 random anonymous non-threaded text-only comments bring?
(Just really curious, I've recently started trying to see things from this perspective and I'm interested in hearing discussion from the business model end)
What kind of value would having a forum user's email address give you? Unless by "monetize" you just mean "send them activity notices so they'll come back", it sounds like you want to spam them.
Personally, I recommend monetizing internet forums by selling people things and having them buy them for money. You can keep interest by just being interesting.
I don't think sending your users emails should be considered spam. Mailing lists and email upsells can be very lucrative, even if you're not emailing users immediately, an email address is a valuable thing to be leaving on the table.
I can tell you that there are a lot of sites I use that ask for my email address and I'd rather not give it to them, and I can tell you that I give them crap. I.e. I give them an address I've set up specifically for the purpose of giving it to sites that require one. There's an awesome, self-explanatory site called 10minutemail.com that I love using; sites can ban their domain (I think some do) (but it's a new one every month), but there's no way a site can tell the difference between my real Gmail account and my crap other Gmail account. And I think a lot of people use similar tactics.
In other words, requiring an email address doesn't mean users will give you their email address. I only give my actual address when I want to. Meanwhile, it's a pain when a site requires one, and sends me an email with a confirmation link. I feel alternately clever (ha, I outsmart them) and sleazy (this probably isn't what they intended), and always annoyed, when I do this.
I recommend making emails optional (but if it has a definite use, like for resetting a password, then explain this to the users). I was happy, kind of exhilarated actually, when I signed up on Hacker News and all it asked for was a username and password; the email address is a text field that one can fill out when desired. I think I remember it explaining that this address wouldn't be visible in your profile; it would just be used for notifications about your account, or something. Take note.
(Just really curious, I've recently started trying to see things from this perspective and I'm interested in hearing discussion from the business model end)