Dave discusses Apple & Microsoft's relationships with developers here
This discussion must include a look at Microsoft's most recent business software acquisitions [ Great Plains & Navision ], products that have historically had many independent developers & VAR's.
One of my neighbors worked for a Great Plains VAR for many years. He expressed great concern about the shift to an ASP (Application Service Provider) model and what that meant for local VAR's and developers. My personal view is that there will always be a need for well trained professionals to help implement, configure and train users, regardless of where the software runs.
I think it will be fascinating to watch how Microsoft/Great Plains and Navision works out with respect to VAR's & developers and how their paying customers react to these changes.
Finally, from a financial standpoint, this market is much larger than chat, photo, dvd and other similar applications. That's why I think it's so interesting to watch.