Brief summary: in this talk I present some work that I’ve done (with collaborators at PARC) related to social search, or how social interactions and social resources help individual users during search activities. I discuss an unexpected finding from a recent project and discuss how social presence theory may be used to account for information sharing and communication practices in large online social spaces (like social networking sites). However, social presence alone fails to account for the differences we’re observing (as illustrated by how Twitter and Facebook would be categorized as “low social presence” media per Robert & Dennis’ classification , since interactions there occur asynchronously and are distributed through time). I propose a notion that I’m calling “inhabitedness” that may account for social search behaviors (and other information sharing practices) on social networks—it borrows from social presence theory but also takes into account other things (e.g., structures, features, and “social objects” made available on different sites that influence user activities.)
 L.P. Robert and A.R. Dennis. Paradox of richness: A cognitive model of media choice. Professional Communication, IEEE Transactions, 48(1):10-21, 2005.