Advertisers hacking Web2.0 for profit

This article discusses how advertisers are using social news sites such as Digg and StumbleUpon to make new profits. For a price they will guarantee that a site will get a enough thumbs up or votes to generate traffic for that site or story. How many other web 2.0 sites are going to become targets to this kind of advertising? What new technologies can these sites use to prevent these hacks from working? This is a classic game of cat and mouse, lets just hope the web 2.0 sites win the game.