This video includes a few still TV screen shots showing Asiana head on, giving a better context than the surveilance camera video. Obviously many layers of swiss cheese here. 321 stopped before being clear of taxiway (did they report... ?), Asiana received taxi clearance, someone in the right seat failed to look out the window, etc. etc. etc. With the complete chaos on the IST ramp the only surprise is that it does not happen more often.