Super-ventriloquism is actually a power that Superman has demonstrated on countless occasions - both back in the early days of the character and as recently as 2005. He has used the ability for a number of reasons. For example, he has made it seem as though a statue of Julius Caesar was talking to talk to a man who said "great Caesar's ghost" too often. He has also sent messages across long distances - to Krypto, for example, like in the above picture - by throwing his voice so that his enemies don't know the source of the voice. In a way, the power makes sense as it could be an extension of his super-breath. If people can throw their voices in the real world, someone with a more powerful ability to exhale should be able to throw theirs further. Still, it's quite bizarre that DC have found so many uses for it!