For the purpose of this blog-post let me focus on Anthony Giddens' book 'Modernity and Self-Identity', which was published in 1991 and therefore preceded the whirlwind social phenomenon of the Internet and the World Wide Web by a few years (See also Alain Touraine's 'Can We Live Together' from 2001, as well as 'Risk Society: Towards a New Modernity', by Ulrich Beck, 1992)
Giddens claims that Modernity, as an historical epoch, started out with a blind faith in the rational capacities of the human mind. Both Descartes' cogito ergo sum and Kant's sapere aude!, should be considered founding blocks of the enlightenment and thus modernity, testifying to a fundamental belief in the ability of the mind to create order, and ultimately control over our environment.
As modernity progressed, Giddens says, this unwavering faith became the subject of radical doubt. All assumptions about the world were possibly faulty and incorporated enormous risks that had to be taken into consideration before any action was taken. Giddens states that "modernity institutionalises the principle of radical doubt and insists that all knowledge takes the form of hypotheses." Witness the birth of the hypo-deductive model in natural science research and the move towards positivism in the human sciences. August Comte has a lot to answer for...
Giddens maintains that Modernity therefore is a reflexive project at heart, and that "the self, like the broader institutional contexts in which it exists, has to be reflexively made. Yet this task has to be accomplished amid a puzzling diversity of options and possibilities." In order to navigate this treacherous terrain, Giddens suggests that the subject has to invest fundamental trust in processes that affect its life, but that are outside its own control. Cue wider social networks and societal structures. This trust is always accompanied by a calculation of risk, and these two elements symbiotically constitute the framework within which the self produces a narrative about its own cohesion and independence.
As an example, consider the amount of trust we have in airlines and their ability to fly us safely to where it says on the ticket. Or how we trust the companies that hold our information online, not to mention the trust we place in the integrity of our friends and our employers to treat our lives with respect and care.
The individual balancing of everyday trust and risk is an essential framework for our understanding of the way we use social media. In particular, the way we go about risk management is often reflected in the way we actively create and maintain an ongoing story about our lives online. Be it contacting an ex for the purposes of rekindling a relationship, or posting a new CV on Linkedin to get a job, our actions are all part of a larger process of life-management, of creating a story about ourselves we can comfortably live with. To maintain such a story is directly linked by Giddens to the formation and maintenance of what he calls 'ontological security'.
Very briefly ontological security can be described as the basic trust invested in the world by the individual from birth and through its consequent socialization, that in turns is needed to carry out the simplest of acts, and normally resides away from the conscious state, as long as it does not feel threatened or is actually ruptured. Modern life constantly challenges this sense of security through its inherent riskiness, but is countered and upheld by the constant reflexive work of the individual.
To keep an active and continued presence on Facebook, or similar sites, is in very important ways therefore not only about play and games, or trivial time-wasting, but about performing essential 'reflexive work', work we do to manage our lives so that we feel safe and sustained and understood day by day.
When the self is constructed through an ongoing process of reflection, online environments provide the perfect arena to build and test that self. Social media strengthens and extends the processes inherent in the social roles of traditional communication media by letting communities of peers directly inform us and situate us in a flow of culture, as well as letting us identify ourselves back to that world, and thereby allowing us a space in which to create and negotiate relatively stable selves.

I am tempted to say "that would be an ecumenical matter" ;-)
This reminds me also of Victor Frankl, who writes about the possibility of finding meaning, though perhaps not ontological security, even amid extreme suffering, such as the Holocaust, which is also part of the dark side of modernity.In a way, ontological security is as much a luxury as physical security and property rights, so it is worth remembering that many people, even in our own society do not find it, on Facebook or elsewhere.
Interesting provocation, as Olivier might say.