I think that the reference of previous landlord is the last resort after you can't pull the credit report. In other words, if you can't pull the guy's credit report or they refuse to let you do it, you'd better not rent your house to them.
Look, you control the quality of your own tenants, if you don't do your homeworks and let the bad tenants in, 99% is your fault, not the other people's fault.
Va_landlord, you are the veteran of this business, you should know much more than most of us. am i right?