I’d have to say Tufte’s just wrong. I’ve seen several of these text-only-cram-it-in sites, and they make it harder to find stuff. Like everything, there’s a balance, but subtle visual cues and good use of negative space get the user to their data quicker every time. The problem is these solutions get ‘bottled’ so quickly, then re-used without thinking about their application.
Digg is a good example- tons of content, but enough space and color to get an idea of what’s going on instantly. But witness the crop of copy-cat sites trying to apply the concept and failing, either because implementation is poor, or because the whole concept doesn’t apply in their situation.