Morons And Their Mobile Phones

For all the good uses of mobile phones, like any technology, it appears that morons will use it for their own reasons as well. Hot on the tails of all those happy slapping stories, comes the news that people are downloading a menacing voicemail message and recording it on the voicemail of others. The message is of an angry guy saying he found the phone number on his wife's phone, and was coming to hurt the phone number owner. It's a stupid kid's prank, but police are apparently so annoyed by reports of it, that they're threatening to prosecute those found guilty of leaving the message. Still, you have to wonder how people who receive this message don't know it's a prank, as shouldn't they have the caller ID of the caller logged in their phone?