Re: long cables
Long video cables are useful. Most video extenders are very limited in resolution. You could run one cable to your TV from your PC in another room and have a virtual "PC under the TV". It's silent with no-compromise on performance. The cable might be expensive, but not as much as a separate media server.
It makes sort-of-remote terminals with proper graphics possible. One PC can service a whole workgroup or house with full-speed video. Multi-seat PC's become a reasonable proposition, especially as multi-core CPU's become the norm, lowering latency problems. Again, you don't have to consider compromises, which makes the idea saleable.
The tech might also make it possible to expand clusters. Where two servers of the same sort are talking to each other, linking them directly rather than buying four 10Gb/s for the servers and four 10Gb/s ports on a switch might be rather attractive. The obvious application I would see is state-sync for clusters where speed is preferred over general connectivity options.
As has been mentioned, SAN is a nice option too. With these speeds, booting off a network SSD could be available to consumers and provide a boost without having to resort to a 20-disk RAID 5 system.
Proper external graphics cards might come into play. I don't think the current ones have particularly good performance (IIRC).