In dry weather on good roads I usually only use my front brake. In wet weather or if mud, gravel etc. is present I'll use both brakes fairly evenly. With modern brakes the maximum braking force achievable on a bicycle is limited by the high centre of mass and short wheelbase causing the rider to go over the bars, not by braking power or traction.
While there's no doubting the front only approach is best for an emergency stop I wonder if it should be used all the time, given that most brake applications are rather lighter.
From a wear and tear viewpoint on the brake levers, cables, blocks and rims it should even out - only using the front will double the rate of wear at the front while the back will last forever (compared to 50/50 use) but what about the fact that the entire stopping force is passed throught the forks and headset? Also, is this suitable for a laden bike where the forces are greater but the weight of the rear end is increased? And what about the increased heating of just the front rim?