Well I've traded tons of pets for stones. If you're trading stones for stones, it gets a little riskier since you have to each make characters on other realms. But honestly...since this isn't against ToS, it should also be protected under ToS. Meaning...if you have a verbal agreement on what to trade, and they don't follow through, you contact blizzard and they will have record of your conversation. It's the same as trading mats to someone via trade chat for a craft. If you hand them mats and they walk away without crafting, blizzard will probably hand them a ban of some length. Blizzard is very keen on protecting the integrity of their in-game mmo atmosphere.