I realized as I wrote this that it was way too long for a single blog post, so here it is in bite sized chunks.
Steve Theodore's article "Who Among Us Shall Build This Shader" touches on a bunch of important issues that come up when game artists start creating shaders for your project. Artist-made shaders are possible these days thanks to the programmable shader capabilities of modern GPUs and by the introduction of visual tools for creating shader programs, usually node-based shade trees. The reason it is desireable to have artists create shaders is it shortens the art pipeline - instead of an artist trying to describe the look they're striving for to a graphics programmer, now they can create the shader themselves using a friendly GUI tool.
This is still a fairly technical activity, requiring a good understanding of the fundamentals of computer graphics and real-time rendering. While not every artist will be able to jump in and create great shaders from day one, the code-writing barrier is pretty well gone. And so they all lived happily ever after...
...or did they? You'll have to wait until tomorrow to see. :-)