Impact of Removing Registration: 250,000 posts
lukew.com
lukew.com
edit: the above refers to an automatic spam-killing filter, and nothing else. From what I saw, at least.
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Some numbers:
Behind registration: ~4.5%, out of an estimated 125 posts/day * 31 days ≈ 174 spam posts over 31 days = 5.6 spams per day
No registration: An anemic estimate of 1% of spam killed, out of an anemic estimate of 2,000 posts/day over the rest of the graph (2000 * (108-31) * 0.01) ≈ 1540 spam posts over 77 days = 20 spams per day
Removing registration lowers spam? Not really. Comparatively? Yes, because you have more non-spammers, and registration is not a barrier to entry for a spammer. But it doesn't reduce spam, and non-spam quantity is not equivalent to quality.
I'd be interested in a moderator-killed post number, weighted against the users/moderators ratio. I'd bet it skyrocketed - anonymity is fertile ground to flamebait.
Topix.net forums on fire: the Ni-chan paradox (2006) http://blog.topix.com/archives/000106.html
He has his own website, where he talks about lowering the barriers to participation: http://shii.org/knows/Anonymous
Although I also don't see what it has to do with this. Removing names isn't somehow more anonymous than just allowing no name. (And having a random name is the same thing as no name. Slightly more interesting too.)
(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)
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.
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.
In order to try to keep the quality of the content relatively high on those sites I also do some very simple statistical analysis on the text of each post/comment. It works very well! I've had one of the sites up for over a year and haven't had any real problems.
There is a Rails plugin that I wrote for implementing a comment system without registration here: http://github.com/aarongough/has_threaded_comments
And that system integrates automatically with my system for doing statistical analysis on the text: http://github.com/aarongough/validates_text_content
Examples of both in use can be seen at: http://whyiamangry.com/
Additionally it allows people to identify themselves as the OP when posting comments, and allows people to be more expressive by giving themselves a name to match their rant like 'AngryAtSuchAndSuch'.
The pseudonym is not optional.
The majority of spammers do leave a valid (free-account) email address and register to spam (probably not used to a forum that doesn't require registration).