“Simplicity” gets a little confused and mashed up, methinks, because: it depends on what you’re talking about, the information landscape(s), the mission(s) at hand, and the desired result(s).

Copy? Simple = good.
Information? Simple / clear = good (though not too simple)
Maps for achieving results? Clear = good (because simple may not be possible or good).

These guys do a good job with process and organizational visual mapping: http://www.xplane.com

And who deosn’t love: http://www.edwardtufte.com
Excellent topic he covers: data density