This isnt good.
"Holy crap. It seems that Google is going to have some pretty serious explaining to do this morning, as one of our readers has sent us in a tip that reveals a major security flaw involving Google Voice. After entering “site:https://www.google.com/voice/fm/* ” into Google, our reader was shocked and discouraged to be greeted by 31 voice mail messages belonging to random Google Voice accounts. Clicking on each revealed not only the audio file and transcript of the call, but it also listed the callers name and phone number as it would if you were checking your own Google Voice voice mail. We’re not too sure if this flaw is something new or if it has been around since Google Voice started, and could just be test messages, but needless to say the matter has to be fixed if it’s legit. Some censored screenshots are after the jump.Thanks, Brian!"
Random users Google Voice mail is searchable by anyone? : Boy Genius Report