Social objects, for example in social interaction design or in the enterprise, are those things around which collaborations and networks form – online they might be such things as blogs, photos, Facebook postings or web clippings. These are at least ‘real’ objects in the sense that Winnicott used to distinguish object-usage from object-relating. Winnicott argued that in surviving its destruction by the subject as a basis for object-relating, the object is established as being ‘external’. But what makes these external objects social is the way they are taken up as the basis of reciprocity or mutuality in the manner of Freud’s third identification.
Jyri Engeström was at the epicentre of the use of this term, but he refers its meaning to the work of Karin D. Knorr Cetina, in particular her papers on “Sociality with Objects” and The Market as an Object of Attachment”. Karin argued that instrumental objects had to be distinguished from knowledge objects. Instrumental objects formed part of an increasingly mechanised and commoditised world that were experienced as complete in themselves, while knowledge objects were experienced as complex, question-generating, endlessly unfolding and incomplete. Unlike instrumental objects, which supported an action-oriented approach to the world of doing and accomplishing, knowledge objects supported an meaning-oriented approach of reflexive experiencing, feeling and remembering. Knowledge objects supported an object-centered sociality referred to by Jyri as a world of social objects.
In explaining the basis of knowledge objects, Karin argued that the ‘real’ object came to serve as a social object to the extent that it supported a being-in-relation, mutuality or reciprocity between individuals on the basis of enabling temporal synchronisation or on the basis of establishing a shared temporal immediacy – individuals able to collaborate around a shared task, or individuals able to be present to each other in some situation (in contrast to the more familiar spatial synchronisation and immediacy of a face-to-face meeting). Furthermore, to the extent that this mutuality was experienced, it was experienced as a ‘We’-ness embedding the individual in a larger context, but derived from the nature of the shared situation rather than from an institutional affiliation. And its efficacy in serving as a social object depended on there being a fit between the nature of its incompleteness and the individual’s own experience of lack – an identification between the individual’s lack and that of the object.
The Kleinian object, then, is a way of speaking about the organisation of the individual’s primary process; the ‘real’ object is established as external, becoming a knowledge object to the extent that it is experienced by the individual as incomplete; and the ‘real’ object becomes a Lacanian social object qua symptom to the extent that it become identified with the individual’s experience of lack.
 The quote is from Winnicott, D. W. (1969). “The use of an object.” International Journal of Psychoanalysis 50: 711-716.