You're forgetting that the 4th quarter of 2009 was the quarter where they sold the most iPhones, ever.
EVER.
And they still didn't manage to retain their market share. And you call that poor performance ? Yes it was poor, but that's only because the competition did phenomenally well. Also, as handset makers move to the different smartphone platforms, the market is going to get very big, very fast. If you look at the numbers in the overall cellphone market, Apple is single digit. Once the entire market has transitionned to smartphones, Apple is going to need a new metric to seperate their offering, or they'll show up as a very thin slice in marketing pies.