I'm not trying to brag -- just giving a data point which seems to suggest that the tagline "nobody reads much faster than 400 words per minute" is false.

I read the first article you linked to. I measured myself on it and got 630 wpm. (And I backtracked a couple times during the reading process. It's hard to focus when you know you're being measured)

I'm by 40-50% the fastest reader I know, except for my father (we're about equal; I've never measured much, just read over his shoulder). When other people read over my shoulder they rarely get farther than through the left page before I'm turning it; most of them only get through 2/3 of the left page.

In a line such as the following (from the first linked article):

  several words. This is called a "fixation," and it takes about .25 seconds on average. You

My eyes seem to fix in four or five spots (I can't tell for sure): "several", "this", "and", "seconds", and "you". So I think I can instantly read about 3 words at a time. When I stare at "called" I can read the whole phrase from 'this' to 'fixation' without moving my eyes. I get the sense that other people only read one word at a time. Is that true for you?

(Edit: In a monospace font like it appears here, I seem to fixate on every other word, so it's more like 8 fixations across the line. The tighter font on the original page seems to let me read faster.)

I was reading before I turned 2 years old, which is pretty young, I think. I am guessing this had something to do with how fast I read, although genetics may also be related.

Edit 2: I should point out that I've never tried to study speed reading or improve my reading rate. I did play around with Spreeder and I could read every word at 1200wpm, but my comprehension was in the toilet. I played around with setting it at 800 (with 4-5 words per screen) and it worked reasonably well, although I never fully got past the distracting element of it flashing lots of stuff in my face while I was trying to concentrate.