If you catch a home run ball hit by the visiting team, you are allowed to keep the damn ball. Why these people throw the ball back on the field and why game attendees (they are not fans) urge them to do so baffles me. That's a piece of the game's history you hold in your hands. It's most likely a very infinitesimallu small portion of baseball history (unless you happen to be at a game when McGwire, Sosa, or Bonds is about to break or set a record). But dammit, keep a hold of that piece. It's much more valuable and sane than Jeff Nelson's bone chips or Luis Gonzalez' chewed gum.