Apple is very proud of its achievements, and in Q4 of 2009, the iPhone achieved something it hadn't done since Q4 of 2008. The device lost market share.
The iPhone's share of the worldwide app phone (nee smartphone) sales market slipped to 16.6 percent, down from 18.1 percent in Q3 of 2009. It's not that the device wasn't selling a lot; according to the Wall Street Journal
, its 8.7 million in sales was 18 percent higher than Q3.
However, overall the app phone market grew 26 percent in the same quarter, as multiple Android devices were introduced and Nokia, seeing a strong comeback, boosted its sales by 4.6 million alone.
Still the rise in iPhone sales can't be ignored, and as another iPhone refresh nears (mid-year, most likely), you can expect the excitement among iPhone fans to reach a fever pitch.