There's a list of thousands of email-password combo on pastebin, free for download 'till removal.
It looks like the data were leaked by a 3rd party chat server which stored logins and passwords in plain text, maybe at each user login request to the main youporn server (there are multiple entries of the same username-password combo).
People with teh bad habit to use the same mail-password combo are urged to change all their passwords around. People who used a primary email account (IE: known to real life peeps) to register there should be prepared to face teh backslash: as usual data posted on the internet will never go away
Info: http://www.databreaches.net/?p=23397
pastebin: eh eh (look for "youporn logins" over there)
(Update 2012-2-23 15.55 UTC+1 : added screenie with obfuscated email logins)