@TimHarford answers a reader's letter in his Financial Times Dear Economist column: "Why do cafes offer free wireless if I'm not allowed to use it?"
The reader complains about being politely asked to vacate a table at lunchtime, so that more paying customers could be accommodated. Should the coffee shop offer wireless internet access if it isn’t willing to accept the opportunity cost associated with it, rhetorically asks said reader?
As a matter of fact, the wireless is irrelevant. The problem of customers hogging tables for hours existed long before computers. The scarce resource (especially at lunchtime) is the table. (Especially the table next to an electricity socket.)
As Tim points out in his column, the lunchtime opportunity cost of letting someone take up a table for four is substantial, while the wireless access, cheap to provide at any time, is a side-issue. But Tim is more polite to his reader than the reader probably deserves, and he fails to point out the false premise in the question. Of course the customer is expected and encouraged to use the facilities of the cafe (table, wifi, toilets) as well as helping herself to milk and sugar. But there is an implicit notion of proportionality: you don't walk off with half a kilo of sugar; you are allowed to use the free wifi, but that's not an unrestricted right; and buying a single cup of coffee doesn't entitle you to sit there all day. (There is a similar dispute about the ethics of making Ghetto Latte.)
Even impoverished writers, who try to make a cup of coffee last as long as possible while writing the next Harry Potter, are aware that there are limits. JK Rowling herself says on her website "the best writing cafe ... has staff who don't glower at you if you sit there too long" (Places to Write). In other words, she doesn't think she has an automatic right to sit there too long, and she appreciates those cafes that tolerate her stretching the limits.
As a non-economist, I'd like to draw attention to two aspects of this. The first is the readiness of Tim and his readers to frame the consumption of coffee and wifi as an economic transaction. "I bought this coffee with free internet access, and I'm entitled to my economic rights." There is no sense of a social relationship between the cafe owner and the customer, or the idea that the customer might vacate the table at lunchtime before being asked, out of consideration for the cafe owner's ability to make a reasonable living.
The second is the irrelevant foregrounding of the wifi issue, suggesting that the reader wishes to see internet access as a primary economic issue. Perhaps this reader is one of those who would make a fetish out of net neutrality, and would see any restrictions on internet access (including this dastardly cafe owner denying me free and unlimited wifi) as a gross violation of some fundamental principle.
See also Ghetto Wifi 2
In January 2014, a flurry of press stories about a radical new way of solving this problem. A cafe in East London (called Ziferblat) now offers free coffee, free biscuits and free wifi. You pay for the time - 3p per minute.
Sources: Ziferblat website, Daily Mail, Daily Telegraph, The Guardian, Time Out.
See also: @BBCNewsMagazine, The Etiquette of Coffee Shop Lounging (16 Jan 2014)
See also @BBCNewsMagazine, The generation dependent on the phone charger (15 March 2014)
Update 15 March 2014