You hear them all the time these days. In the closing days of any major political campaign in the US (I’m sure to some extent this is true in other places in the world, I just don’t have any direct experience), the attack ads. If you listen carefully, you’ll hear a few voices who dominate that scene. NPR has an interview with a couple of the major players in that corner of the voiceover business on their web site.
My thanks to my friend Steve Knight for sending along the link.