You may have heard about the angry Philadelphia Phillies fan who, at a game in Miami on Sept. 5, confronted a father, accusing him of stealing a home-run ball from her and giving it to his son, inciting an internet furor.

That came days after another sports-related internet uproar: A business executive from Poland was caught on camera taking an autographed hat intended for a child at the U.S. Open. After a social media backlash, the man, Piotr Szczerek, apologized.

Then there is the report from Page Six of a woman biting a child in the Hamptons over a T-shirt that was shot out of a cannon at a free concert in August, part of a weekly summer series.

If it seems as if adults have forgotten how to behave at public events when presented with the prospect of a freebie, it’s hard to quantify. People have long dived into the stands to capture a wayward foul ball or headband thrown into the crowd by an N.B.A. player from the tunnel.

As Jocelyn Saber, a former Boston Celtics cheerleader who tossed free swag to fans, put it, “‘Free’ flips a switch in people’s brains.”