What techniques do you use? I read at around 600wpm, and increasing it by 50-100% seems pretty daunting.
For a hacker, it is normal to not subvocalize.
I think it is also one of the reasons that we hate meetings so much. An email can be written at about 40 wpm, and read much, much, much faster. So past 2 or 3 people, the dominant strategy should be text, unless sidechannel meaning is needed (where emotions are involved or whatever).
That's been debunked a while ago. There's no such thing. http://en.wikipedia.org/wiki/Subvocalization