One reason he gives is that there is too much data on the page. Tufte has said having a lot of data isnt the problem (humans are excellent at scanning images),

One reason he gives is that there is too much data on the page. Tufte has said having a lot of data isnt the problem (humans are excellent at scanning images), terrible design is the problem. Since I suck at design though I tend to need to do simpler charts. :)