CBS and Viacom, the media company that owns MTV, Comedy Central and Paramount Pictures, both got letters from National Amusements this week telling the companies they should think about getting back together. When Viacom and CBS split in 2006, it was predicted that Viacom would be the stronger company and CBS the weaker one, when in fact it's gone exactly the opposite direction. This encouragement comes as Shari Redstone, Sumner's daughter, has fully seized control of the board. The key to the deal actually happening is a personnel issue -- who would be the CEO of the new mega-company? The obvious answer is Les Moonves, the current head of CBS, but for the moment at least, he's playing the part of the reluctant bridegroom.