I remember back in the CV/Atari/Intellivision/etc. days people routinely swapped games back and forth for a few weeks that they had gotten bored with for other games from their friends. This was when new games cost a bundle and before the wide spread rental of cartridges.
Since the carts were so durable there really wasn't worries about damage and I don't recall anyone too concerned about labels since half the carts had the owners name or initials on them.
I did however almost loose a CV Galaxian since a lot of time had passed, I was into the C64 and when I finally got back to my buddy I found that he had traded his whole ColecoVision and about a dozen games (including a Xonox double ender and my Galaxian) for a well used Sony Walkman to someone else. He got it back and returned it but that was a close call. I had no idea of rarity at the time (1980's).
I'm guessing that many gamers here were active "temporary" traders?
I wonder if with the threat of disc ruining scratches and all the rental places if this is still common with the current system generation users?