IMHO the electrical difference between the multiple switches that we are discussing and a ring circuit is the 'loop area'. Loop area means inductance in the circuit where substantial energy can be stored in a magnetic field. This means increased circuit inductance and production of external EMFs. Switch loops do not add 'loop area', because current flow in one conductor is balanced by current flow in a matching adjacent conductor.
In the UK, 'ring circuits' are specifically permitted to be protected at a higher current level than 'spur' circuits of the same gage. The NEC has no provision for this, so this 'benefit' of ring circuits would not be found in an NEC compliant installation.
In the US, a 'ring circuit' would need to comply with 300.3(B); in a ring circuit you _explicitly_ don't have all conductors of the same circuit in the same raceway.
I believe that a ring circuit, using non-metallic wiring methods, and protected as is normal for the given conductor size, would meet the requirements of the NEC. I also think that it would be a bad idea from the point of view of emf issues, and would offer little benefit because circuit ampacity could not be increased.
Thinking about it some more, I belive that a multiple switch installation could easily run afoul of 300.3(B). If you ran a feeding circuit to a couple of switches, and then separate switched feeds from the multiple switches to a single outlet, then not only would you have parallel electrical paths, but you would also have conductors of the same circuit in different raceways, as current could go through one switch leg but a different neutral conductor. IMHO this would again be allowed using non-metallic wiring, but a bad idea because you are introducing large loop area in the current flow pathway.
On the other hand, if you ran all of the switches as switch loops, or ran one switched feed and the other switches on a loop of that first switch, then I wouldn't see a problem. 300.3(B) does not explicitly permit switch loops, but switch loops are clearly allowed. Running these switches as switch loops does not introduce significant loop area.
-Jon
