We already heard many stories of iPhone developers hitting the jackpot with little Apps for the iPhone. The NY Times has published another one about the iShoot developer and how he made $800,000 in 5 months.
If the other mobile App stores like the BlackBerry App World and the upcoming Palm Pre App store cannot deliver these kinds of stories they will have a problem.

These developer success stories are gold for Apple. If individual developers can make that much money, companies can make even more.
The new iPhone 3.0 OS beta has 11 pages for Apps and looking at the full pages of Apps on the current 2.0 OS, they are going to need more than 11 pages. The iPhone App store is an extremely frictionless market. All competitors need to be able to recreate that if they want to succeed. It is a bit like Amazon.com and the rest of the ecommerce landscape.
Photo shows the must have iFart App for the iPhone.