So how do you handle the case of a non-techy user who logs in and wants to upload some pictures? They have to go to Flickr (or equivalent), create an ID there, come back, and link that new ID to the social network feed? Or do you end up providing that sort of service, too, in addition to the option of using an external service? If so, how is this better than a Facebook app that lets you feed your data from an external service into your feed?