though the question is: was it ever alive?
the answer is yes, in that flickr had stumbled upon facilitating such a situation. Social Photography is facilitated by a site where the user has a photo used for currency, and people can act in a social manner on the photo. typically, this is by views, faves/likes and comments. subsequently, there was a curating effect, self-serving or altruistic, via invitation to groups.
that social photography was a success in furthering photography, or perhaps trivialized it, is to be another (long) conversation; or even that social photography was engaged by a significant number, or a critical mass, of "true" photographers is yet another conversation.
social photography thrived through the rise of flickr and its peak, before an anecdotal decline — and many reasons seem to contribute — which allowed other sites to rise and be noticed. this period was from 2005 to about 2007, or 2008 at the latest. there is no clear demarcation of when social photography "lost it", and this is not of great concern, though it is sensible to argue that the rise of Instagram marked its death. the change in platform, from flickr's desktop to Instagram's smartphone, propelled the change in what a photograph is among people.
someone may think: « but Instagram raison d'être is that of social photography! »
not quite. Instragram is not social photography, because there is no engagement about photography. yes, a photograph is created for the purpose of a social interaction, which is in line with previous mechanism, albeit at a much smaller scale and perhaps not involving so many strangers. thus, there is nothing photographic of merit in Instagram. that is, aside from the photographer putting as much, or little, effort into taking and processing the photo — in third party apps — but not in enriching that experience through a social interaction. while Instagram had to solve a photograph-storage/servicing engineering problem, Instagram is about sharing/connecting and not photography — this according to one of its founders. still, we must remain aware that despite a company's intentions, people can morph the intent of a website to their needs. this clearly happened with flickr.
while this generalization can benefit from a longer discussion, and definition of terms, the important observation is that it has created (at least) two notable groups: the Social Photographer, and the Longform** Photographer. ( a person can fit in either, or both.)
the Social Photographer is working the social sites, notably tumblr and Instagram, and amplifying it through social networks, notably twitter and facebook. the interactions of faves/reblogs, short platitudes — such as the infamous "great capture" — and comments is the gained currency from mining the right photo. there is much to be enjoyed in this realm, if one finds the proper content generators. the photographic qualities of the photos are secondary, or non-existent.
the Longform Photographer can be working within the social network tools, but seeking a different way to communicate — perhaps often frustratingly so — and requiring more than mining socially-appealing photographs to build an audience. actually, an audience is required by any photographer type, but the required audience count threshold may be lower. this Longform Photographer may reside somewhere in between the Social Photographer and the traditional art-world photographer.
clearly, the author is in this latter group... and in the process of learning, and figuring out how to use the internet to help a photographer's, and a photographic, pursuit. the audience is less of a concern at the moment, since much is to be figured out. this site is an aid towards that pursuit.
** a commonly used term in online journalism is "longform journalism" , and The New Yorker has references to "longread" articles.