If you consider that Slashdot's advertisers include the likes of Microsoft, then this list of their poster's e-mail addresses is a very valuable Google search indeed:
"by * 0..1e+07 * gmail|hotmail|yahoo com|org|net on" site:slashdot.org

http://www.google.com/search?num=100&hl=en&lr=&client=safari&rls=en-us&as_qdr=all&q=%22by+*+0..1e%2B07+*+gmail%7Chotmail%7Cyahoo+com%7Corg%7Cnet+on%22+site%3Aslashdot.org&btnG=Search

Whatever address obfuscation system they are using is not being applied very consistently.

yeah thats a pretty nasty thing to be left open!1

It looks like more people on /. is using Gmail than Yahoo and Hotmail.

Or you could try http://www.google.com/search?q=%22by+*+0..1e%2B07+*++com%7Corg%7Cnet+on%22+site%3Aslashdot.org&btnG=Search&num=100&hl=en&lr=&client=safari&rls=en-us&as_qdr=all

Or http://www.google.com/search?num=100&hl=en&lr=&client=safari&rls=en-us&as_qdr=all&q=%22by+*+0..1e%2B07+*+*+*+*+net%7Ccom%7Cjp%7Cit%7Cde%7Cedu%7Cfr%7Cnl%7Cau%7Carpa%7Cbr%7Cuk%7Cpl%7Ctw%7Cca%7Cmx%7Cse%7Cbe%7Cfi%7Ces%7Cus%7Cch%7Cdk%7Cno%7Cat%7Cru%7Cmil%7Corg+on%22+site%3Aslashdot.org&btnG=Search

Slashdot has an option to "Show your real email address without cowering behind childish anonymity or obfuscation." but I doubt many people actually selected it. My own address is presently listed in those Google results (although I have now disabled it on Slashdot)

Since obfuscation techniques are applied randomly to each shown address, you only have to look through a small sample of slashdot e-mail addresses in order to learn of all them.

Here are the techniques you have to decode:

userdomain.com
`moc.user' `ta' `domain'
userNOSPAMdomain.com
userdomain.cLISPom minus language (LISP, COBOL, etc...)
userdomainQUOTE.com minus punct
userdomain...com
user AT domain DOT com
userNospAm.domain.com
(user) (at) (domain.com)
[user] [at] [domain.com]
user&domain,com
userdom3.14ain.com minus pi
userdo[ ]n.com ['mai' in gap]

This is security by obscurity at its worst. What is the use of randomly inserting LISP or COBOL into such a lame obfuscation technique?

For those that read this far, here's the code I used. It's only two hours away from having every single e-mail on slashdot: http://pastebin.ca/309575

This is possibly even worse on Wikipedia. If you "Enable e-mails from other users," there is a special form that you can fill out that does not expose that user's e-mail address to you. But if you then check "Send me copies of emails I send to other users," then the e-mail address is available as plain text in the copy of the e-mail you receive.

An e-mail harvester would only have to create a dummy account and cycle through every single account, trying to send e-mails.

The example queries of Brian Mingus and Jake's View include information about the Safari browser...

google . com/search?num=100&hl=en&lr=&__client=safari&__
etc.

It doesn't affect to the results, but Google get information about Safari clients when people click these links, and they are not Safari users ;-)

And I am actually using Konqueror, not Safari :) I used to strip all that out, but why bother?

I'm using Firefox...

I use Firefox when I can, but right now I am on the Kubuntu live cd.

Brian can you explain the "0..1e+07" part of your search query?

Brian, this was only related to statistics collected by Google. You can forget the issue!

It's just an expression that says "match any number."

Technically, it's:
0..1.797693134862e+308

(Returning 17 billion docs)