The abundance of dark fiber is the result of fiber network build-outs that included laying substantial extra fiber-optic cables at the time the trenches were opened, as a non-specific plan for the future and as a hedge to limit the likelihood that new trenches would have to be dug. I emphasize the availability of this commodity to make the point that new forms of communication that require incredible bandwidth are viable now because of the absurd availability of nascent bandwidth infrastructure.
To fill this bandwidth, many things are possible, with more in the future. Video telephony is one obvious opportunity. Videophone capability can be done and is being done in 3G networks around the world already.
But with the amount of available bandwidth, one can consider not just video telephony as per 3G networks, but multi-channel, HD-quality video telephony. Multi-channel video, along with some substantial, local image processing, allows for some very interesting things, such as 3D or interactive scene “fly through” at the control of the receiving end. This would be interesting for extended family interaction at the holidays, but if such a service becomes available, who knows how it will be used? Another application I have heard a lot about is in the medical field. 3D medical-imaging devices, such as Tom Cruz’s baby sonogram, can send streaming, ultra-high-res images to a remote facility, which could control the instrument remotely. Remote medical procedures like this are being used hospital-to-hospital even now, but they are viable over the Net to the home in some neighborhoods without additional infrastructure, due to the abundance of the dark fiber.