While social networking sites have no problem attracting members, making money off those users is proving to be a bit harder. That's not to say they're not trying to find new ways.

While larger sites such as MySpace and Facebook have made some inroads in monetizing their massive membership, even they are a hard sell for many advertisers worried about having their ads next to "inappropriate" content, CNET explains in a longish analysis piece. But social-networking sites are beginning to explore technologies that target users and provide them specialized ads based on their interests.

Aggregate Knowledge, for example, targets "affinity groups" or clusters of members of site members who share common interests. These groups could be clustered based on group/forum memberships or shared interests listed in their profiles. Still, even this method poses problems, and advertisers might be more willing to invest in methods they are more familiar with.

"Before we see sophisticated databases that are applying social mapping to ad display and selection, we'll see something much more basic, like funneling people into channels that advertisers already understand how to buy," explains Mark Pincus, chairman and cofounder of social network Tribe.net.