Off-topic: By all means, charge the $99 for distributing on the App Store, but I am not really sure why Apple doesn't allow for Apple ID level verification for personal apps. Something similar to the mobile provision they use right now, e.g. having Xcode generate a binary that is associated with the same Apple ID as on the iPhone.
I don't think that would work because setting up a shared Apple ID using a throwaway webmail account would be trivial. Each one would be good for multiple devices, and running a build script to generate multiple binaries for multiple accounts wouldn't be all that hard.
They used to ask for a credit card, but I believe that's no longer required (if it were, you could just use a prepaid gift card).
