Today at Apple’s iPhone-for-Business Event Steve Jobs announced figures for the iPhones market penetration

28% of the smartphone market and incredibly represents
71% of U.S. mobile Internet usage.

Source WSJ Live Blogging at the iPhone-for-Business Event

Apple also annouced it’s iPhone SDK (Software Developers Kit) as part of the new iPhone Enterprise Beta Program.

Added:Engadget has a great slide show of the iPhone SDK Press conference.