Interesting. I think there are some potential circumstances where this would be acceptable.
For example, when I go to restaurants on a busy night, there's often a wait. I usually go to the bar and grab two drinks, pay by CC, and close it out. I do this with the expectation that my table will be ready by the time I'm ready to order the next round, and I don't want to burden my server with having to swing by the bar and close out my tab for me.
Another time I might see this as acceptable is when there are two or more people in a group, and each person is buying rounds. I'll buy a round on my card and close it immediately, knowing the next guy will be buying a round later. I'm not going to leave my tab open, because I might not ever get a turn to buy another round, and I don't want to hassle with hunting down the bartender and closing it at the end of the night.
What I find very odd, though, is bar owners and bartenders who seem upset that somebody would do this, even if they intended to buy two more drinks later. Sure it's inefficient, and I can't think of any reason I'd ever do it outside of the circumstances I mentioned above or something similar-- but the bottom line is that your business and your livelihood depend on the customer's money. Customer service is your job, even if some customers don't make it as convenient as others.