... then you are probably using a commercial hot-spot, or maybe someone has tried to provide some "security."
The last couple of days gave me a chance to experience a variety of Wi-Fi setups. Besides the generally working open conference network at WOS (hidden behind a NAT box, of course), there were the insecure, but cumbersome security mechanisms at TU-Berlin (ultimately circumvented for many people in the room by setting up a laptop as a router between an ad-hoc open network and the official Internet access), and airport Wi-Fi at CGN and TXL.
CGN is in T-Mobile's hands. The design of the payment process looked reasonable, at least as long as you are a T-Com or T-Mobile subscriber. Random 404 errors and wrong host names in SSL certificates (hotspot.t-mobile.net vs. hot-spot.t-mobile.net) pointed towards a rather unprofessional implementation, though.
(The Vodafone setup in MUC about which I ranted in March had a more cumbersome billing design, but was implemented better.)
TXL (where the photo was taken this morning) is more open to a number of wireless providers. Access points are shared between providers; users are then supposed to pick providers from some web page. When trying to go further than that, I got inconsistent and irreproducible behavior, including 404 messages, transparent proxies complaining, and timeouts. The "wlan-zone" was useless for me.
Open and free Wi-Fi should be a convenience at airports -- spending the waiting time attempting to debug a network is not a productive activity at all.
