Right now a large portion of Reddit is willing to jump the ship at all cost. You can't design for such events, i agree, but if you had a perfect reddit clone right now - people would flock even if there was no content. This is a digg moment. The problem is scaling up when there's demand, because people don't like lag and a half loaded tab. No one is stepping up as a Reddit successor because everyone know they have no pockets to scale to Reddit scale