I never paid too much attention to Vine, because I never-to-rarely use Twitter to begin with, but this seems rather remarkable. I guess since people already knew what Vine was, maybe it caught on really quick. Maybe Instagram folks are just very excited to over-share some more.
One way or another this begs the question: is this the bleeding-edge testing the waters (i.e. should we expect massive amounts of future adoption as it proves itself) or is this the maximum userbase and can we expect usage to slowly taper off as people get bored?