Facebook pages strike me as the digital equivalent of a typical ritual people engage in in real life: put up a front that indicates to external observers that you are intelligent, funny, popular, loved, important, etc. for the purpose of attracting mates, using positive feedback about the mask you've put on to build/reinforce your perception of yourself such that the divergence between the two is reduced -- all the while hiding any of the doubts, discontent, and other honest feelings that are natural to living life. I surmise a significant portion of this identity building/mate attracting ritual is subconscious and can be given an evolutionary glean.
It strikes me as very fake and I dislike people who are obsessed with it -- women moreso than men, I'm sorry to have to say. I'm surprised the facebook version of the ritual would generate more envy than in real life, however, since it seems so obviously fake (huge friends lists, 'likes' and other such artificial bullshit) so as to be laughable. People's real life masks can be much more convincing, at times blending in with who their true self such that it's impossible to differentiate the two (for a time).
I have a fake Facebook for the sole purpose of launching occasional spank bank enhancement excursions, and none of the info I see makes me envious (wow, 1,427 friends!) because I'm confident it is an illusion in the sense defined above, and even if it weren't, it's enough work managing my own life let alone analyzing others'.