I believe than anyone should be able to write code!  It is fun to get into the flow of coding and even more fun to see the end result: a working program.  I have seen instances where the code was much more complicated than it needs to be.  This makes me wonder whether the original author was in a rush, was working late at night, or just plain wanted better job security for being the only person capable of understanding and changing the code.

Code should be written to be as simple and as easy to maintain as possible.  If performance issues appear after the code is delivered, and adding complexity can increase efficiency, then that is fine!  

But it is crucial to realize that if no one else can understand the code, then all I can say is, good luck trying to make it run faster!