While I was watching the Yankees at Atlanta Braves game last night, the commentator stated that he just saw a fan fall from the upper tier at Turner Field. The commentator stated that he felt that the game would be ended, however, surprisingly the game continued on as if nothing had happened, although paramedics attended to the mortally injured fan - http://www.nydailynews.com/sports/baseball/yankees/fan-falls-upper-deck-yankees-braves-game-article-1.2341840 (caution, gory details are in this story).
The Rogers Centre seems to be a place where such an incident is just waiting to happen with its high 500 level and steep tier. Do any stadiums employ netting under high tier levels to catch falling fans? There have been so many incidences of fans falling to their death that I wonder why more isn't done to design stadiums for fan safety? I found this undergraduate study on fan safety (well done for an undergraduate report) - http://fisherpub.sjfc.edu/cgi/viewcontent.cgi?article=1038&context=sport_undergrad