BizWeek's got a story about how Facebook and Comcast are teaming up with a skilled video producer to create and package a series called Facebook Diaries. Basically, it will be a series of user-created videos that are then edited, packaged and probably enhanced by producr RJ Cutler, the Emmy-award winning documentaryproducer who created American High.
This little story captures some tremendously shrewd ideas:

• Let the audience use the new tools to make the content
• Hire an expert to organize, package and enhance what they create
• Use the means of distribution (the social network) as the marketing tool to build a viewing base
• Market to the audience (who are also the creators) on the front end as they make and upload the content, and on the backend, as they watch the finished shows
• Create groups and social networks based on the content they create and market through those too.

Voila, the ecosystem of targeted, viral marketing, recreated--with a per user acquisition cost waaay lower, bet, than most.
And it's focused on that 18-24 demographic.
And anyone can play, assuming they have a critical mass.

flickr travelogues anyone?
Yahoo Personals date documentaries?

You get the drill.