What's most interesting here to me is that people are taught which fingers to type with. I was never explicitly taught how to type, but I usually hit 6 with my left middle finger. I type at 130 WPM on average.
Edit: after some screwing around, I hit every number but 1 with my middle fingers (I hit 1 with my left ring finger).
Do you still type 130wpm if you are typing a lot of numbers? I'd be surprised if you could reach those speeds while typing all number keys but one with a single finger.
No, if I'm typing a lot of numbers I switch to the numpad. If I had to use the number keys along the top, I'd be much slower than 130. Numbers like "130", though, I just noticed that I distribute the keys among several fingers. I'm not sure of the rules my fingers are following in that respect. Examining your own typing habits is fun :)
Edit: after some screwing around, I hit every number but 1 with my middle fingers (I hit 1 with my left ring finger).