I don’t know what the chances are of a tennis ball landing in the audience, but I would think that people could keep these. They go thorough a lot of tennis balls in a match.

Professional football players frequently through balls into the spectators. Also if a football is accidentally thrown or kicked into the spectators then it would be very hard to get it back.

If you find a golf ball after a player has dropped a replacement and taken a penalty. you can keep it.

@LostInParadise At tennis events, the balls need to be returned. There’s a limited number of balls in play at any time, and there’s an art to monitoring how they wear out and when they get replaced.

The first time I went to a tennis tournament, I was surprised to see this happen – an official stands at the sideline, with arms up and waiting for the ball to be tossed back. My tennis-playing husband explained it all to me.

Thanks for the correction. Darn cheapskates.

Bikers discard their bottles all the time (although this year the Tour de France apparently is outlawing that)

Paintball.