Michael DeGusta via Technology Review
[…] smart phones, after a relatively fast start, have also outpaced nearly any comparable technology in the leap to mainstream use. It took landline telephones about 45 years to get from 5 percent to 50 percent penetration among U.S. households, and mobile phones took around seven years to reach a similar proportion of consumers. Smart phones have gone from 5 percent to 40 percent in about four years, despite a recession. In the comparison shown, the only technology that moved as quickly to the U.S. mainstream was television between 1950 and 1953.
Almost as fast as TV, which was artificially delayed by WWII.