Here’s an article on BBC about the wifi trial at Charling Cross tube station in London:
I think this is the next step that highlights the significance of Internet and its role in today’s society. If it turns out fine, this can open up another opportunity for advertisers. It’s true that most people have smart phones with 3G connection but I believe that the wifi connection provided underground in the station will probably work better. However, connecting to a public wifi connection might lead to certain security risks for mobile phones.