From marbles to baseball cards, from Beanie Babies to Pokemon cards, children have historically found collecting and trading objects appealing. If your child's interests lie in collecting leaves in the fall, or rocks in Central Park, you probably haven't given much thought to their collections, other than that they may be dirty and clutter up their rooms. On the other hand, if your child's obsession leans toward the $150 "rare" Beanie Baby or Pokemon card, collecting and trading takes on a whole different meaning, and parents need to be informed about the benefits and pitfalls of this "got to have it, got to trade it" game.