A friend of mine's take on the rollback.
If one person buys something from a bugged vendor, then goes to check out a baking vendor in PoK, which some poor schmuck finds when he comes along to buy a muffin, realizes he has the wrong vendor and moves on to the next one, then goes off to the Bazaar to eat his muffin and go look for some nice haste item so he can eat his muffin faster, goes to the trader, realizes he doesn't have enough money, runs to the hub to sell a blue diamond he's been saving for a rainy day, then goes to buy his haste item, while another fool comes along and finds this sweet blue diamond on a vendor, buys it and puts it on his trader, and then you come along and buy it for 400PP to complete your Grandmaster's Baking Spoon ... well, everyone in that chain is now infected, including you, and you will be rolled back. Any money, exp, items or hair you gain, you will lose. Any NPC you touch from then on has the blight, and they will gladly spread it to every single player that buys stuff from them, and they will in turn infect every player they interact with.
You think the bubonic plague was bad? Imagine getting the piece for the mage epic in Plane of Sky off of a freakin' drake on steroids, then come to realize that because the druid who handed you 3 copper for a key (because you forgot to bring money, you stupid git) had sold a foraged vegetable to the muffin man, and now your crown of eternal flame and cinder fury is missing from your inventory, and so are the 3 freakin' copper!
Inside each person lives two wolves. One is loyal, kind, respectful, humble and open to the mystery of life. The other is greedy, jealous, hateful, afraid and blind to the wonders of life. They are in battle for your spirit. The one who wins is the one you feed.