New iPhone software could be delayed
http://www.guardian.co.uk/business/2008/feb/26/apple.apple

Apple is rumoured to have delayed the launch of the software tools that will help third party developers produce independent applications for the iPhone and iPod Touch. Apple is currently updating its US online store in advance of the release later on Tuesday of a range of new products, believed to be upgrades to its MacBook range of laptops. Further details of the SDK are also expected to be announced.
Although Apple wants to broaden the appeal of the iPhone and iPod Touch by letting other people design compelling applications which users can put on their devices, it is very mindful of the need to protect consumers - and its own reputation for high security - from viruses and malicious software

Also Apple could also make use of itunes if it were to distribute to third parties, but also this could also lead to a loss in customers