I'm in college so I don't have that many direct connections and its how I have managed to stay in contact with people from summer work. I'm not sure how it will scale for me in the future.
But I'm *awful* at maintaining friendships, networks, and things for that nature. So I'm not a good person to take advice from on this.
I'm in college too, actually, I've found facebook to be a good networking tool, especially some of the the global groups (there are a few good entrepreneurship ones), I've made some interesting connections through it.
But I'm *awful* at maintaining friendships, networks, and things for that nature. So I'm not a good person to take advice from on this.