[AT&T] activated 2.7 million iPhones during the quarter…Apple [announced] yesterday that it had sold 8.75 million iPhones overall during the quarter
via AT&T Activates 2.7 Million iPhones in Q1 2010 as Growth Slows – Mac Rumors.
About 31% of the units sold in Q1 were activated on the AT&T network. The iPhone is reaching a more balanced global distribution but still has a long way to go.