I'm currently involved in a project where a number of iPads loaded with a special app are given away to a number of people at a certain event. Both because of time constraints as well as our desire to give these people a really exclusive app, we decided to prepare these devices using ad hoc installs of the app.
What will happen to the app when the recipients of the device decide to sync it with their existing iTunes account instead one of our "recipient x" accounts?
The application will stay and will work.
If they will sync the applications then your application will also be saved on their iTunes, but they won't be able to sync the saved app to any device that is not listed in your provisioning profile...
The application will work - until ad hoc distribution provisioning profile expires.
You can also deliver updates via email or "secret" website for both application and provisioning file, if you believe your users are able to install them by themselves. Just wondering, where and when is this event you give iPads away...