As part of a scheduled upgrade on the Tokyo to Osaka line in 2009, Internet access over Wi-Fi will be added: The bullet trains will have service at 300 km/h that's brought onboard via leaky coaxial cable, a way of pushing out high-frequency signals over wire that can be picked up by onboard receivers.
The timeframe and the plan for wire to be involved seems quite odd when there have already been successful tests of high-speed wireless transmissions to trains, including one by a vendor which is part of a test for California's Capitol Corridor train line. They were able to pass signals at 320 km/h.
great. Now I'll have to buy seat belts for my laptop too!