Scoble has a great couple of podcasts today on Social Graph based search. He talks about how new social based search plays are resistant to SEO (Search Engine Optimization) and are eventually going to kick Googles ass.
This is exactly the basis of what Lijit was founded on. The idea of social trust being the major driver in judging the value of content is spot on.
Scoble talks about how Mahalo is a social graph based search because they have content editors that are part of their social graph. I think the example is a little broken in the Mahalo case in that the graph is not really naturally occurring. In other words the graph as selected based on social popularity, who wants the job, etc. perhaps not actual expertise in a specific domain. He also suggests Facebook is in a great place to capitalize on their large social graph to revolutionize search. I agree, however Facebook is still a walled garden of content. If Facebook would extend their social reach (and content reach) beyond their walls they would be in a great position.
Lijit is using the naturally occurring networks that already exist out on the web to create powerful search from the ground up. We don't hire content editors and we don't force editors (publishers) into any specific social network. We use the networks you have already built to power the world's most powerful foundation for search.