I've been trading since I was a kid. Whether it was hockey cards, recess snacks,
Magic cards, Pokémon cards or
pogs, we were always trading something.
There was a tacit understanding that the buyer-beware policy applied when making a trade. But it was also understood that it was bad practice to take advantage of an ignorant trader. No one liked situations where a kid went home to boast to their older brother about a trade, only to hear he'd been duped. It inevitably led to a big argument the next day: "I didn't realize the card I gave you was so good. No fair — I want it back."
Should a kid who unknowingly trades away a valuable pog be able to undo the trade? This was one of the tougher ethical questions we dealt with on the playground. You shouldn't make a trade if you're not sure about it. But on the other hand, if you didn't understand the trade you were making, how can you consent to it?