If I asked you to define simplicity in the context of design, your definition would likely include at least a general principle of using fewer parts/elements rather than more. MIT's John Maeda touches on this in his blog, Simplicity:

"Simple parts are most simple when there are few (versus many) parts. When there are fewer parts, there is an opportunity to distribute one's precious time in fewer directions which results in a higher quality per part."

                                                 — John Maeda, MIT

Steve Wozniak, of course, was famous for slaving over his early designs in the'70s and getting them to work with fewer and fewer parts. The fewer the parts, in general, the cheaper a design (a product, a system, an event, etc.) will be. But another real advantage is that the chance of something going wrong, of failing, is reduced.

Few versus many parts. I was reminded of this aspect of simplicity of design when I was out running the other day. Thirty minutes into my run, and 5-6 kilometers away from my home in central Osaka, part of the heel of my right shoe suddenly went bouncing past me while I was jogging easily on a smooth surface. Weird. I never had part of my shoe just fall off like that before. Now minus the right side of the 2cm heel, continuing to run was not only uncomfortable but also dangerous. Frustratingly, I had no choice but to walk (limp) home. The shoe had only about 50K of wear.

   
Above: Here are my shoes placed on my desk at home moments after I returned  (of course I cleaned the outsole first; we don't allow shoes even on the floor indoors here, as you know). As you can imagine, running on that heel was out of the question.

I was wearing Nikes with the "Shox" technology, the TL3 Shox. "Shox" are little rubber columns on the outsole of the shoe that actually work extremely well as shock absorbers. The particular shoe that I was using, however, has one especially hard piece of rubber attached to the column on the outside heel. Nike calls this BRS 1000 Carbon Rubber for the "key wear areas" of the shoe. This is good for people like me who have a slight supination in their form. It is interesting that the failure of a small rubber part can make this pair of $150 shoes completely useless as a running shoe in just a blink of an eye. This little rubber part is ironically the "Achilles heel" of the shoe. And since I have already severed my right Achilles tendon twice (years ago while playing American football), a strong, elevated heel is very important.

      
Did the designers of this running shoe stop to consider that runners run on trails and beaches or roads, etc. far away from home or their cars, often miles away from anyone at all. The possibility of the shoe failing is usually the furthest thing from a runner's mind. The shoe was a given...at least they used to be. This important part on the Nike shoe was held together with only a bit of glue over a small surface area (since the "shox" is a hollow piece of rubber the area where glue can bond is limited to the rim). I didn't know it at the time of purchase, but only the integrity of the glue for this piece of rubber stood between me and a possible running injury.
    
In the "old days" of running shoes (such as the '70s era Oregon Waffle above) the outside tread was usually a single bonded piece of rubber. If the glue ever failed it would do so gradually, noticeable first along the edges. The failure of the bond would not lead to a "catastrophic failure" of the shoe during the middle of a run. Today the sole of a running shoe may have 2-3 (or more) pieces of rubber attached in some way, but usually these pieces are not so small that they could be easily knocked off, nor are they in such a crucial area as the outer heel. The BRS 1000 heel is 2cm in height; a loss of the heel makes running unwise at best. I will glue the heel back on, but I will never trust this particular shoe again for anything but walking. I bought the shoes in Hawaii; I doubt Nike here in Japan will take them back.

I am thankful for the advancement in running-shoe technology since the days of running track as a high school student. But I would hope that the advanced designs they create would not lead to an increase probability of failure as well. Is this an inevitable consequence of complexity? Maybe Nike needs to ask how they can leverage their technology and cutting-edge design to produce a running shoe that is supportive, good-looking, and will absolutely not fall apart in the middle of a run. Maybe they can take a tip from the folks who designed the Jackson manual typewriter over 100 years ago. I love these lines from the people who brought you the Jackson:

On Simplicity:

"As every one knows, the greater the complexity of a machine the greater the liability to derangement, and the greater the outlay for repairs."

On Durability:

"Mechanical simplicity is naturally followed by mechanical durability."

Not every problem lends itself to simple solutions, of course. Still, as "simple as possible" and "with as few fill-in-the-blanks as possible" is a good general principle worth aiming for. I'm not suggesting we go back in time and use typewriters and run in Oregon Waffles, etc. But whether we're talking about hardware, software, user interface, presentation graphics, or running shoes, simplicity is not only aesthetically pleasing, it often leads to better performance, greater reliability, and overall better results.