So Apple really really want to make sure you paid the $99 to develop iPhone app on only ONE machine

I had iOS 5 SDK installed on Mac OSX Lion Preview, so I was all fired up to do some development, particular when I just got my new iPad 2 I brought mainly for this development effort.  Then, the deployment to the iPad 2 gave me headache.  After 2 hours of frustration, I found out that I have to revoke the old certificate and use the OSX Lion to regenerate a certificate again.

That's when I realized that Apple is really trying to make sure that the US$99 you paid for the development privilege works only on ONE OS environment.  If you several Mac OSX environment on your machine and you have multiple XCode installed in these environments, only ONE can be used to deploy to your devices.  Apple does that by having a public private key installed in your OS and make sure the development certificate only works with that key.  Yep, Apple goes so far to make sure that they got your money.  Good job.