I have predicted before that Social Networking sites will end up being more important than search engines. They have huge followings and traffic with MySpace reportedly already having twice the traffic of Google's search engine. Instead of searching for sites in a search engine many people now search for them at their favorite Social Networking site.

Some Social Networking sites such as MySpace are already showing PPC ads from major PPC engines like Google. Others are likely to monetize with some combination of major PPC engines, their own ads, or in unique new ways.

I only recently came upon a site that is very similar to Google Adsense. Users upload their videos to Revver which attaches ads to them and then pays the video provider a percentage of the ad revenue.

There are so many Social Networking sites already keeping up will be a challenge. I'll add more reviews that explain the differences as I come across them:

Social Networking Awards

Speficially about StumbleUpon