There's little doubt that sports are good for the bodies and minds of people who play them. For people who watch them, though, sports are a negative. Never mind the enormous amounts of money consumed every year by soccer, football, baseball, basketball, hockey and all the rest. Never mind the distorting effects on politics of favoritism for sports franchises, whose economic payoffs are always exaggerated and often non-existent. Instead, just consider all the injuries, mayhem and occasional deaths directly caused by sports fandom. This morning, Vancouver certainly is.
The Boston Bruins weren't favored to win their last game against the Vancouver Canucks for something call the Stanley Cup, which is the shiniest and most important of the hockey doodads. According to this study (pdf) of college football, upsets are associated with the largest spikes in post-game assaults and other violence. It didn't matter whether the home team won or lost in an upset, according to this work, by Daniel I. Rees of the University of Colorado. Something about the "wrong" team winning seems to license a sense that life's normal rules are suspended.
More in line with most people's intuitions, and Vancouver's experience, this study by David Card and Gordon Dahl looked at police reports after Sunday football games in the United States. They found that "upset losses by the home team (losses in games that the home team was predicted to win by more than 3 points) lead to an 8 percent increase in police reports of at-home male-on-female intimate partner violence."
No doubt the Vancouver riot will lead to calls for better controls on alcohol, more civility from fans, yadda-yadda-yadda. I'd like, therefore, to state the obvious: Big-time sports franchises waste resources, screw up urban life, and trigger violence. Society would be better off if the whole apparatus didn't exist. (I know; we'll sooner see world peace and the end of human hunger before we get rid of all these bowls and cups and pennants, but being hopeless isn't the same thing as being wrong.)