You guys are thinking in todays terms. Think about tomorrow...
The dispensaries that sell black market weed will be busted first. Thats too easy. The feds walk in and ask to see the books and they will figure it out fast. In fact, they will have their case built before they walk in the door. Boom. Closed. Licensed lost.
No legit dispensary will risk that.
Sharing an ounce. Sure. Nobody cares about that. But get caught carrying more than an ounce on ya and there is the excuse for a search warrant. Then they come to your house and what do they find? Either a case worth pursuing or not.
Again. This is nothing new. Booze is one example. Cigs are another. Intellectual property is another. When big business wants their interests protected they will buy the politicians they need to make the laws and pressure for enforcement.
Wait and see. The old days are gone... or rather they will be shortly...