I think in a microcosm, 'username' is just shorthand for how active and aware you are in the startup community as a whole. It's the same as everything else, if other people in the industry remember you, whether from a mixer you attended, or an article you published or what have you, you are much more likely to have an 'in' with them. Is it a means to an end? No, but it is a useful and helpful artifact of being interested and active in the field you want to go into.