The artist (or the article) suggests that the pictures he took on the metro are the 'real' person, whereas the pictures on the social site are the 'ideal' person. I'm not so sure. I think its very possible that the person in the social network photographs is actually far closer to the person they really are than the photo of them riding alone on the subway.
Further, the artist is clearly curating what he shows and what he doesn't and likely has his own message.
(I really like this sort of "subversive art", that has deeply important educational aspects showing people how the world really is in interesting ways...)