Are you a Yahoo Voices user? If so, you need to jump online right away and change your password because it may have been compromised. Not only were the password stolen, but email addresses for every user of the service was posted, so it is not even necessary for someone to figure out the email associated with the password.
The people responsible for posting the 450,000 passwords call themselves D33Ds Company. They claim they posted the information contained in the file in not meant to serve as a warning for any greater attack, but rather as a “wake up call” to the people at Yahoo.
The D33Ds Company claims that there are “many security holes exploited in web servers belonging to Yahoo! Inc. that have caused far greater damage than our disclosure”. Posting passwords online might not be a good thing for users of the site, but it could be worse. There could have been exposure of payment information or social security numbers.
They actually say that they are posting this information to protect users from further damage that could come from the vulnerabilities. It’s possible that they could have chosen a less drastic way to get their message across than making the passwords public.
Again, if you use Yahoo Voices, change your password now. If you are one of those people who use the same password for multiple accounts (which is not a good idea), then you should also change any other accounts that use the same password.