CL Sholes invented the QWERTY keyboard layout for use in mechanical typewriters, where metallic letters swung forward to strike inked tape, leaving the letterforms' shape on paper. The QWERTY layout prevented the letters from jamming in the strike area as they swung from their seated position into their strike position. QWERTY has been used as an acceptable keyboard layout since the 1870s, and continues to be the default layout today even though we no longer need to prevent metallic keys from jamming.
In Diffusion of Innovations, Everett M. Rogers documented how University of Washington Professor August Dvorak invented an alternative to QWERTY in 1932. Dvorak's studies lead to a keyboard design where a majority of typing could be done on the home row, whereas the QWERTY keyboard requires users to move more frequently across top, middle, and bottom rows in order to type words. Dvorak's keyboard solved a problem on the user end, allowing weaker typists to quickly peck out words, whereas Sholes' solution solved a mechanical problem on the hardware end. Wolfram's Letter Frequency interactive demonstration by Frederick Wu illustrates this principle nicely, showing the frequency of keys used on each keyboard. Advantages aside, DVORAK never succeeded like it could have. In their book Design and Technology, Suzanne Strazzari and Deborah Trevallion point out one of the key issues revolving around the DVORAK keyboard's failed take off: bad timing. In the 1930s, typists had already grown comfortable with using the QWERTY layout, and worse yet, DVORAK hit the market during the middle of the Great Depression.
QWERTY continues to be an accepted and default keyboard layout when we now have touchscreen keyboards for pecking away words or customized features like Swype for dragging out words. To date, DVORAK keyboards have not caught on, despite their advantages. But as new devices enter the marketplace, with easily-customizable keyboards, such as touchscreen tablets and phones, a new generation of typists may be right around the corner. I wonder what Siri would say if I asked her which keyboard I should use.