"Yeah, but so am I." I responded.
Now before you write me off as just a smart-ass, let me explain. I knew that what he meant was "isn't that box on the front aerodynamically inefficient?" And he is right - it is. If you can change the aerodynamics, you'll go faster. But that won't be easy. Because YOU are the biggest inefficiency on the bike.
Consider this, lowering your posture by using aero bars on your bike reduces your frontal area from 4.2 square feet (an average of riders in an upright touring position) to about 3.6 square feet. This will save you about 30 minutes up to an hour on a 200 kilometer ride. If that's important to you.
And that's where the 23mm width nylon tires meet the road. (In fact, my tires are nearly twice as wide. More inefficiency, I suppose.) If the question posed by my friend, who understands the need for speed - he's an IronMan - was in fact only about aerodynamic efficiency, then my answer stands. However, that box on the front is VERY efficient if you want a bag which is waterproof, and which can keep your nutrition, first aid, camera or phone, or any other goodies right in front of you where they are easily accessed without taking the time to stop. In that case, the bag is very efficient.
Rear pockets on jerseys are handy, but getting stuff out of them with full fingered gloves on is nearly impossible. And forget about using the rear pockets of a wool jersey! I purchased my first wool jersey this year and the first thing I noticed about it was the elasticity of the fabric when wet. As soon as I began to sweat, it began to sag. And with my rear pockets full, it sagged even more. In fact, the back of the neck of the jersey stretched so much, that it looked like I was wearing it backward! Good thing I have a very, very hairy back, or I'd have had the mother of all sunburns down the middle of my back. In fact, it stretched so far that when I was off of the bike, the contents of my rear pockets bumped into the backs of my knees when I walked, threatening to buckle my legs and knock me down unceremoniously on the gas station parking lots.
I don't need to be fast. I need to have stuff handy (and I need a wool jersey without rear pockets). If that 30 minutes that the bag costs me on a 200 kilometer ride ever starts placing me in jeopardy of DNFing most rides, then it will be time to pack it in, move to Rhode Island and focus on trying to beat Jennifer Wise at Cribbage. (I hear she's a Massachusetts record holder for most games won while manning a control on the Boston-Montreal-Boston 1200 kilometer ride.) In the meantime, I'll just carry the essentials in the most efficient way I can, and get used to being given the "last rider" award at the RUSA events I enter.