6 Drink Minimum at neighborhood bar?!?

There is a casual bar by my house that has been in operation in the neighborhood for 27 years. They are changing their policy that every patron in the bar has a 6 drink minimum. You get a card with 6 boxes on it and with each drink you get the bartender punches your ticket. The bouncers will not let you leave unless all 6 boxes are punched. Is this really a good idea??