Purpose and Strategy For Building Mobile Apps

Josh Bernoff in his book Empowered, has a good chapter on the purpose and strategy for designing mobile apps.

The purpose of building mobile apps is to increases sales, improve loyalty and reduce costs. He also points out an interesting aspect of mobile app design. You cannot have a single design for the Blackberry and the iPhone.

Companies have found out Blackberry users have different habits compared to iPhone users. The design of your mobile applications will depend on your user base. He even suggests that a company should build a mobile website first, analyse the devices used to access the mobile web site and then design and build native apps for specific devices and user habits.

Sounds like a good approach to me. How do you approach your mobile design strategy?