As noted at Daring Fireball and others, Apple has made the following change in their iPhone Developer Program License Agreement.
3.3.1 — Applications may only use Documented APIs in the manner prescribed by Apple and must not use or call any private APIs.
The fact that Apple refuses to allow me to install software I write onto the iPhone 3G that I "own," has already convinced me to not purchase another iPhone (or iPad), but this change makes me want to immediately blend my current iPhone just so I don't continue to add to the statistics Jobs uses in his keynotes to demonstrate the iPhone's popularity.
I'm a large fan of the hardware Apple puts out. The iPhone, iPad and Macbooks are all fantastic from a hardware viewpoint. But as AAPL has exploded over the past decade, Apple has been getting more and more brazen in their lock-in policies. Now, not only does Apple want to control the hardware platform and software platform, they also want to dictate the tools that developers use to perform their work. That's just unconscionable.
I really wanted my next laptop to be a nice, new unibody Macbook Pro (to upgrade my early 2008 model), but unless Apple makes a pretty hard about-face on this, I'll have to vote with my wallet and take my business elsewhere.