Water, food, shelter, wireless... In the last year I've passed through a dozen airports, and my search for free wireless at many of them has been fruitless. This possibly incomplete list of airports worldwide shows that most of the busiest airports aren't on the list. Of the fifteen busiest airports--measured by passenger traffic--travelers only get free access in Hong Kong, Atlanta, and Las Vegas, assuming this list is accurate and up to date. To be sure, many regional airports in the U.S. offer free wireless, but I think it's because they're less likely to serve travelers with large expense accounts. O'Hare, LAX, JFK, Denver, and San Francisco, by contrast, all offer wireless for a fee, and appear to reflect the pricing practices of hotels. Many mid-priced hotels offer free wireless, but if you patronize pricier properties, watch out. (Last summer I stayed at a hotel in New York that charged $7 for fifteen minutes of access in the business center!) I suspect airport executives, like those of pricey hotels, know that a certain percentage of their customers need--or think they need--services like wireless, and are willing to pay steeply for it. I don't know if administrators of busy airports actually see wireless as a "profit center," as high-end hotels do, but the pattern suggests such thinking.
Also: Salon recently published an article on "good" airports, and "bad" airports around the world. The approach isn't particularly scientific, just reader responses, but worth a look if airports and air travel catch your fancy.