The iPhone has only been around for four years, but in that time more iPhones have been sold than all the Macs ever sold in Apple’s entire history.
The total number of Macs sold in 28 years is 122 million. In 2011 alone, if you tally up all the iOS devices including iPods and iPads, 156 million were sold—more than all Macs ever sold.
The iOS platform as a whole reached 316 million cumulative units at the end of last year.
By the way, which word you would use to describe the steepness of iPhone's graph....
I think even 'Skyrocketing' wouldn't do justice.