I2's speed is achieved by using 10 different wavelengths of light over a fiber optic cable, with plans to eventually use 100 wavelengths. Each wavelength can carry 10 gbps. While the incredible speed would be especially helpful to corporations with large data transfer needs, there has also been concern about its use for good ol' fashioned piracy. The RIAA and MPAA both were apparently afraid enough of I2's incredible bandwidth that it filed hundreds of lawsuits against students attending colleges where I2 is being used. That'll teach the kids to pirate those movies! Yar!
Fiber Optic Cable image courtesy Raymond [GNU, 1.2]