Why do I always get punctures in my rear wheel? I get probably five times as many punctures in my rear wheel as opposed to my front wheel. I run a good pressure and don't get obvious pinch flats. 

Does anyone have a logical reason why this could be happening?
The back wheel is the wheel bearing most of the weight and also the wheel providing the driving force. For these 2 reasons it is likely that the forces being exerted between the wheel and surface are much greater on the rear wheel than on the front. This makes it more likely that you will get punctures on the rear wheel than the front - all other things equal.