Starbucks and the Tragedy of the Commons

My wife and I were killing time in two separate branches of Starbucks yesterday. In my branch, I noted a man who had taken over a window table by covering it with a huge laptop, books, files, newspapers and a token coffee. He regarded the place as his office. My wife, at her branch, had seated herself at an empty, four-seat table. A man called to her that this table was being 'held' for somebody. She rose and went over to his table, another four seater occupied by three people plainly having a meeting - files, papers etc. She sat down at the fourth chair. 'You can't sit there,' cried the man, horrified, 'we're having a meeting and you haven't even got a coffee.' 'I know,' said my wife, 'I'm torn between a latte and an Americano. Should we discuss it at this meeting?' These grade-one-listed jerks then flounced off to the table she had just been told to abandon. She waited for a moment and then left the cafe, the better to irritate these fools. The jerks and Huge Laptop Man plainly thought they had some proprietorial interest in Starbucks' seating arrangements. The company encourages this by providing web access and a policy of absolute tolerance towards long-stay, low-spending, table-hogging customers. But now their branches seem to be suffering from the familiar Tragedy of the Commons phenomenon whereby individuals exploit common resources until they are exhausted or useless. The problem is: how do they relieve their customers of the illusion that they own the joint without compromising their laid-back, corporate style? My solution would be sudden bursts of gunfire.