The Pentagon City mall gets Wi-Fi, free for now: The Fashion Centre at Pentagon City is just one stop from the Pentagon's Metro station and only a handful from the central areas of D.C. The mall's operators will run Wi-Fi in common areas for free initially, and plan to charge $3.95 per hour up to $49.95 per month for access.
Mall-based Wi-Fi access is becoming increasingly common as malls compete with other "third places" (there's work, home, and somewhere else) to draw in customers. If people start flocking to street-based shopping areas because it's easier to do business there, the malls can suffer.
I've found in my research that mall operators typically do a horrific job of explaining whether Wi-Fi is available, where to use it, and what it costs. You'd think they might want to promote it on the Web site as much as in person.
A restaurant in Seattle states it best on their front facade. A banner reads in big type, "Free Wi-Fi is Here!" In tiny letters they add, "while dining."