Social network theory fails to explain why people connect to each other because it leaves out the objects that connect people together. An alternative sociological approach builds on object-centered sociality. Successful Web services build around social objects: Flickr did it to photos, YouTube did it to videos, Microblogging services like Jaiku and Twitter did it to SMS and IM. This talk explains the theory of object-centered sociality and elucidates five principles for designing services around social objects.