Back in 2005, when I was at USC, I created a site called FBookAuction.
The site allowed users to auction off ownership to groups on Facebook. The new owner could send marketing messages to the group. (This was before Facebook apps.)
The idea was to give Facebook entrepreneurs a way to make money by aggregating groups of people that an advertiser would target (e.g. people with allergies). And to give advertisers (e.g. allergy drug company) a way to send marketing messages to their target audience.
It didn’t work.