This came up in conversation recently, and then I re-stumbled upon this wisdom in my text messages from May 7, 2012 while searching for an address and feel it is worth preserving. On the subject of using SI prefixes using Anheuser-Busch as the base unit for "1 brewery":

[Anheuser-Busch in St. Louis] brew on the order of 10^9 gallons per year. We brew 10^2 [a nanobrewery]. I was wrong when I referred to our operation as a picobrewery... That would be brewing a shot glass 1/8 full of beer annually.

I keep thinking that a true picobrewery per that definition would be a hilarious, and possibly awesomely hipster, thing to exist.