Unfortunately i see way to people that are not responsible with their alcohol consumption. I agree that most normal/responsible drinkers will at least wait until they get home to crack open the growler and enjoy, but there also a good number of people that would be coming multiple days a to get a refill (especially if the Coors or similar started offering their beers) and not being responsible . In today's society it seems like it only takes a few bad apples to ruin it for the rest of us. Like i said before the logistics for a small corner store like mine would make this idea nothing but a hassle. This concept would only be viable for the bigger stores and even then would probably present a challenge in-terms of the extra storage needs.
As a store employee I'm technically liable for accident that involves a customer, just as bar tender is technically liable for serving an intoxicated person, so i guess i see too many negatives in this idea.