Human beings are notoriously short-sighted when it comes to weighing the larger social costs of their individual actions - the routine economic argument has been that all these negative externalities need to be priced, which would translate to the true economic cost of individual decisions. Obviously, this has never been implemented in the case of global warming and carbon footprint. Assuming that a pricing mechanism is discovered (it is a subject of hot debate as we speak: http://en.wikipedia.org/wiki/Emissions_trading) there are questions of implementation, enforcement etc. Pretty much impossible to implement/enforce in the current global economic and political landscape.
So what is the way out?
OPTION-1: The Hayekian and the libertarian (they rarely seem to differ) opinion would be to lay the facts in front of the people (i.e. remove information asymmetries) and then leave it to the individual moral standards and the forces of the market to figure out a 'sustainable solution'. Utopian is putting this mildly.
OPTION-2: The top-down approach starting with governments, international bodies etc. coming out with a solution framework. Here again, you ought to be suspicious - what makes these government bodies (even though they may be 'experts') any better at arriving at the right answer? Governments have rarely been able to work together on a bilateral basis, leave alone a global scale - why should this be any different?
So both are equally bad - and then what is the answer? Is there one at all? We all need to be optimistic (what is the alternative?!) Probably some combination of the two (a regulatory body and a pricing mechanism) - remains to be soon what that is and how it will come about.
And so - what is the carbon footprint of this blog? And if I do not touch this blog again and Google does not delete my data, then this blog will occupy some bytes on some storage device unto perpetuity. So what is the true economic cost of all this? Food for thought.