Those wonderful antimicrobial hops. Makes me wonder how different things would be if early brewers used some other antimicrobial agent in their beer instead of hops. Ginger beer, cool. Garlic beer, err...It boggles my mind how easily a single mold spore can find its way into an otherwise sterile fermenter and ruin a beer, but tossing in half a pound of unsterilized hop pellets at the end of primary presents practically zero risk of infection. I've experienced it myself and still can't accept that this is the case.