Totally on point about getting users to actually use it. That's kinda where I'm at right now with what I'm working on, and it's by far the hardest step. Twitter actually had very few users for the first 6 months I believe, but things like Facebook and Instagram were big hits pretty quickly.
Agree with you on Instagram, but Facebook had the benefit of one-at-time rollout to universities, which upped its exclusivity and draw. (Granted it was also good product.)
