This just in:
link
Yahoo Inc reported the theft of some 400,000 user names and passwords to access websites including its own, saying that hackers had taken advantage of a security vulnerability in its computer systems.
Accounts involved are from these sites:
137556 yahoo.com
106869 gmail.com
55147 hotmail.com
25520 aol.com
8536 comcast.net
6395 msn.com
5193 sbcglobal.net
4313 live.com
3029 verizon.net
2847 bellsouth.net
2260 cox.net
2133 yahoo.co.in
2077 ymail.com
2028 hotmail.co.uk
1943 earthlink.net
1828 yahoo.co.uk
1611 aim.com
1436 charter.net
1372 att.net
1146 mac.com
1131 rediffmail.com
1124 googlemail.com
1053 rocketmail.com
928 juno.com
853 optonline.net
810 yahoo.ca
572 peoplepc.com
546 mail.com
536 excite.com
453 netzero.com
433 netzero.net
419 embarqmail.com
400 yahoo.co.id
367 live.co.uk
344 insightbb.com
342 shaw.ca
339 windstream.net
336 inbox.com
336 btinternet.com
322 tampabay.rr.com
321 lycos.com
316 mchsi.com
313 yahoo.com.au
307 netscape.net
302 roadrunner.com
299 gmx.com
298 myway.com
1870 .edu
93 .gov
81 .mil
It appears that perhaps only accounts somehow linked to Yahoo Voices (formally Associated Content) are involved, see
this link for details. On that page, they also link to a text file including the compromised data, of which this seems to be a mirror:
second link.
I am aware that this may change into a "Who uses XYZ anymore?"/"Why don't you use Z?" very quickly, but in any case, if you've been involved here, it may be a good idea to change your passwords.
EDIT: Originally seen on NeoGAF. Forgot to credit the source. Embarassing. I'm sorry!