As an ex bartender/manager that is an interesting way of pulling a pint. Definately a way to regulate any spillage. Those look like plastic cups so I wonder if they are disposable and only good for a one time use. Personally I would fire anyone that handed drinks out by grabbing the rim. Hope he washed his hands when he came back from the bathroom.
Could get a LOT of people HAMMERED in very short order with a system like that!
You'd better be careful to install it at a safe height too. If it was installed too low, some drunk staggering around could decide to take a seat. THAT could get interesting!