Wasn't he asking about how feds find the dispensaries, not the growers? The dispensaries, (god, I can never spell that word), are usually listed with city hall, many pay taxes and all that fun stuff. The ones that try to hide from their city usually don't last long enough for the federales to even notice them. Who knows how they choose which co-op to raid, they'll go after big profitable ones, as well as the ones that are clearly running for non-profit, (the way they are supposed to).