Deemed “the most successful product launch in Apple’s history”, the iPhone 4 has sold 1.7 million units in just 3 days. The 3GS sold 1 million in the same time frame when it was released last year, as did the iPhone 3g. Comparatively, the original iPhone took 74 days to reach the 1 million unit mark. If this same trend continues in the upcoming years, Apple will control a massive portion of the smartphone market. (And will surely have to spread out to more networks)
Please note that the graph does not reflect iPhone 4 sales.