Great thread.
Seems like that the LR' recommendation of chains on the fronts only could be the good old legal liability issue, much like the advice given by most manufacturers about always putting the new tires on the fronts, if bought in set of two, even if the rear tires are more worn out. I read somewhere that this is to fight the statistical data which suggests that in accidents that occur due to loss of control, more often the cause is due to the loss of traction in the front wheels rather than that of in the rear wheels, etc.
I started to research snow chains for my LR4 and came across this thread, very helpful indeed. I was looking at the following accessories pdf on LR site and noticed that they have two different types (one page 5 and page 6), wonder whats really the difference or if anyone here has either of them.
http://www.landrover.com/content/us/accessories-kit-brochures/8-29-13_LR4_10.09.pdf
Also, just a thought, could there be a mechanical/technical or computer control related reason as to why the manual specifically mentions to not to put the chains on the rear? I mean they could have easily said something like that "if you have only one set available, mount them on the front wheels instead of rear". But they specifically mention not to put the chains on the rear wheels.