In terms of loot, making and then breaking a clear in-game agreement on the way loot will be distributed by a Master Looter can be considered a scam. Unfortunately, some players will make loot agreements they have no intention of keeping to get players to join a dungeon or raid group. In these situations, players who disregard the original agreement and then take (or give away) loot in a different way are potentially violating our Scam Policy. If you believe you have been scammed, please contact In-Game Support.So, if you join a PuG, make sure the RL specifies the Loot Rules before you start. If he doesn't, you're on your own. If he does, and there is any kind of Ninja Looting, especially if you are the rightful winner, there is now a real chance you will get your item. More importantly, even if loot has no rightful owner and your RL decides to sweep up the lot regardless, Blizzard should ban him for being a scumbag. The key here is MAKING SURE THE LOOT RULES ARE SPECIFIED.
Please note that if In-Game Support is able to determine a scam has taken place after a clear in-game loot distribution agreement is made, any items involved may be removed from their current owners. In cases where a "rightful" owner can be proven, these items may also be transferred; however, loot will be left unassigned if a "rightful" owner cannot be identified. Due to the privacy associated with these investigations, In-Game Support will be unable to release details regarding an investigation's findings, actions taken, or its final outcome. (Source)
I can think of at least three PuG's I've been in in the last six months where if this policy had been in force, the players would have been banned as a result. Hooray for Blizzard finally making a stand.