It would be perfect to have a small simple and single connection between a laptop, enhanced iPhone/iPod, or *cough* tablet *cough* and an external display (power would be the only other connection needed, unless the proposed connector contains power pins). The display would contain ports for hardwire networks, USB, firewire, speakers, "web" camera, microphone, eSATA, etc. (much like Apple's and others current display products).
This would be Apple's answer to docking stations that often have rather large fixed connector(s) in slots on the bottom side of a laptop. Having a USB like connector gives you more use case coverage then the docking connector solutions currently and could be used by many more form factors other then just laptops.
I am fairly sure this is Apple's main goal with a secondary goal being the following...
As time passed USB, firewire, etc. - assuming adoption - could be replaced by this technology so you would get displays/hubs for this technology... all working with a single connector/cable type (likely will need mini variants). Storage devices, video cameras, video devices, audio devices, and sync targets like MP3 players, etc. would be perfect candidates to switch to this (assuming power and cost budgets make sense).
By using an optical connector you can get longer distances and higher-data rates. Also many more options to improve throughput, etc. as optical transceiver/coding technologies improve without having to create new connector types.
If the communication technology used inherits and expands on FireWire... a single connector could mux several independent streams of data, including timing sensitive streams with low CPU overhead (later obviously would be needed at the data rates being talked about).