Social news sites such as Digg, Propeller, Reddit, StumbleUpon, where the community decides what content is worthy and what content isn't, are powerful enough to drive tens of thousands of visitors to some lucky content producers, and thus have become an incredibly valuable marketing platform. One good day on any of these sites can get you more than 60,000 visitors in less than 24 hours.
A great byproduct of the demographic of these social news sites (many of the users are...